Does CAPT Merchant charge for this service?
Yes, but not for an initial consult. A candidate emails him the facts, and then usually an email or phone response from Capt Merchant is the next step.
My understanding is that he does this in retirement to help cadets out. (He himself had a colorblindness battle with DoDMERB as an NROTC cadet at The Citadel).
I am not a client. My friend (met through this forum) received an initial free phone conversation with Capt Merchant regarding his DS, and has since contracted him. He says that the fee is reasonable and he has been a big help.
The biggest complaint I have read is that because CAPT Merchant is retired and thus travels a lot, he may not always be instantaneous in getting back to folks. There have been more positive posts about him on the forum than negative, overall.
If it were me, I would first try for a local doctor with a military background. If it is ROTC, then the ROO or the recruiting officer can give some good guidance. However many SA candidates have no one to bounce their case off of.
CAPT Merchant fills that need and has a lot more time than Larry Mullen does!
My own DS could have been in trouble because of the way he described a "rib flare." We were fortunate in that our DoDMERB doctor caught this and re-described it on her examination so it didn't pose a problem. However a less experienced physician could have not addressed it, and my DS would likely have been DQ'd.