As everyone has responded , ME FSDO did not do his research.

With a PP Glider certificate, you can act as PIC for solo operations in an airplane with the 61.31 endorsement.
Regardless what the ME FSDO may say, OKC will not issue two active pilot certificates to the same pilot.
OKC will not issue a new student certificate without the PP glider certificate being surrendered.

I caution my glider students, now rated glider pilots about this when they move on to get their airplane rating. I even agree to meet with their airplane instructor to review if they like. Not many airplane CFIs are used to rated pilots coming for private pilot airplane training.

BillT