Step 1.
Let Even E = M+M.
We can construct a set D(1) =

We can designate the members of D(1) as duplexes and can have abbreviation
for each member as dr where r = 0 to M and as such, cardinality
of D(1) = M+1 > M = E/2.
D(1) is the largest possible set from which we have to sort out at least
a single dr such that both r and 2M-r are primes to satisfy the
conjecture.
For this, impliedly, we have to rule out all values of r and 2M-r where r
or 2M-r are composites. Let us formally define dr composite when
either r or 2M-r is composite. Therefore, the whole exercise as such reduces
to sorting out composites from the range of 0 to M as well as from M to 2M
and finally to see if there exists any dr which is not a composite.
For this, we have to construct a chain of subsets of D(1) such that D(2)
contains only those dr's where 2 is not a factor of r or 2M-r and
then to have subset D(3) of D(2) such that for no member dr of
D(3), 3 is a factor of r or 2M-r, and so on.
Let us first of all construct a subset D(2) of D(1) such that D(2) = {dr
| r = odd
M}.
Therefore, cardinality of D(2) shall be
E/4.
Step 2.
Before, we construct further subsets and count their cardinalities, let us
first of all see the following properties of number which may be availed for
the purpose:
a. Let E =
E
E
= A
B.
If A<
E,
then B>
E.
Therefore, in terms of primes 
E,
we can sort out composites uptil E.
b. Let P={p1, p2, p3, ......, pu}
be the set of all odd primes 
E
such that pk < pk+1 for k=1 to u.
Let N is largest odd natural number 
E.
Therefore, 1/
E
< 1/N.
Further, as:
1/N = 1/3
3/5
5/7
7/9......(N-2)/N.
Therefore, if we restrict the denominators (2m+1)'s of
above fractions of the form (2m-1)/(2m+1) only to (2m+1) as a prime, then
1/N < 1/3
3/5
5/7
9/11
......(pu-2)/pu,
as pu is the largest prime 
E.
Therefore,
1/
E
< 1/N
< 1/pu
= 1/3
3/5
5/7
9/11
......(pu-2)/pu.
Step 2A.
Rule "one more than the previous one" gives us a natural number array which
takes E steps uptil E as 1, 2, 3, ......, E.
Rule "proportionately" permits us to cover as a table of p uptil E only as
E/p steps as p, 2p, 3p, ...... p
p.
Taking pr as (r)th prime and pr+1 as (r+1)th prime,
r>2, as such, both odds, shall be expressible as pr+1 = pr+2s
for suitable whole number s and pr+1 
E.
Now, taking A(1) as array of whole numbers; A(2) as A(1) except multiples
of 2; A(3) as A(2) except multiples of 3; and so on, A(pr+1) as
A(pr) except multiples of pr+1 shall be permitting us
to reach at the cardinality of A(pr+1) with the help of the cardinality
of A(pr) as:
1. Total multiples of pr+1 uptil E are E/pr+1.
2. Multiples of pr+1 = odd multiples of pr+1 + even
multiples of pr+1.
3. Even multiples of pr+1 would be multiples of 2 and as such
would be ruled out from A(1).
4. Therefore, at the most, only odd multiples of pr+1 i.e. 1/2
E/pr+1
would remain to be ruled out from A(pr).
5. Taking cardinality of A(pr)
E/pr,
the cardinality after accounting for 1/2
E/pr+1
i.e. odd multiples of pr+1,
we shall be left with E/pr - 1/2
E/pr+1
1/2
E/pr+1
6. The number 1/2
E/pr+1
gives us 1/4
E/pr+1
pairs (duplexes).
7. Now, from here 1/4
E/pr+1
pairs (duplexes), to be back to the array of whole numbers, first we have
to straighten two arrays of duplexes from (1, 2M-1), (3, 2M-3), ...........,
(M, M) to a single array amongst (1, 3, 5, 7, ...........2M-7, 2M-5, 2M-3,
2M-1) and then as a second step we shall be going from above odds' array to
the whole numbers (1, 2, 3, 4, 5,...........,2M). This as such, in first step
would take us from 1/4
E/pr+1
pairs to 1/2
E/pr+1
odds (singles) to E/pr+1 to complete sequence of whole numbers
(odds as well as evens).
8. With this, we can say we have reached from A(pr) of cardinality
E/pr to A(pr+1) with E/pr+1 as cardinality.
9. The odds pairs of E/pr = 1/4
E/pr
to odds pairs of E/pr+1 = 1/4
E/pr+1
gives us a multiplier (pr+1-2)/pr+1 which takes us from
1/4
E/pr
to 1/4
E/pr+1
as that E/4(pr+1) = (pr+1-2)/pr+1
E/4pr.
Hence we can apply the above multiplier i.e. (pr+1-2)/pr+1
and sequentially can cover uptil the largest prime 
E.
Step 3.
Let us construct a subset D(3) = D1 (a subset of set D(2) where
we are sorting out and cancelling dr's of D(2) for which either
r or 2M-r is composite with p1 (first odd prime i.e. 3) as a factor).
We can write M = 3Q+R where Q is quotient and R is remainder obtained of
division of M by 3. Therefore, the composites of the range 0 to M with 3 as
factor would be Q-1. In fact, there are Q numbers which would be having 3
as a factor. But as 3 is divisible by 3 but is not a composite, therefore,
the balance numbers would be Q-1. On the other hand 2M=3
2Q+2R
would imply that 2R may be greater than 3 and as such the total numbers of
the entire range 0 to 2M which may have 3 as a factor may be 2Q+1 but as this
quotient 2Q+1 includes 3 also, therefore, the composite numbers would remain
(2Q+1)-1 = 2Q.
Therefore, the maximum numbers uptil 2M which may have 3 as a factor and
as such would be composites would be 2/3 of 2M. As such, the cardinality of
the set which would remain after cancelling composites with 3 as a factor
would be (3-2)/3 i.e. 1/3.
As such, the cardinality of subset D(3) = D1 would be not less
than (3-2)/3 of cardinality of D(2) i.e.
1/3
E/4.
At a next step, the cardinality of subset D(4) = D2 after cancelling
out the composites with second odd prime i.e. 5 as a factor would be
(5-2)/5
1/3
E/4
i.e. 3/5
1/3
E/4.
Sequentially, we may proceed uptil the largest odd prime pu 
E
and shall be having cardinality of Du, after cancelling
out the composites with all odd primes as
(pu-2)/pu
(pu-1-2)/pu-1
....
3/5
1/3
E/4
1/3
3/5
5/7
7/9......(N-2)/N
E/4
1/N
E/4
1/
E
E/4
E/4
2
for E
64
E=p+q for E Even
64
can be physically tested on the lines: