Since you hold a 1600 ton inspected license (uh, excuse me "officer endorsement") there should not be a tonnage limitation on your MOTV. It sounds like a NMC eff-up. You should probably give 'em a call. I've got Master 1600 Oceans and MOTV Oceans and there isn't anything on my STCW limiting me to uninspected towing vessels <200 tons. This crap is driving me nuts!