278 to 180 in 7 months on reta is in the top tier of responses - the lean mass preservation question is the right one to ask at that pace. The 153lb lean figure held from 257lb to 238lb is the critical data point; tracking it through goal weight is what separates a good outcome from a great one.
HMB-FA is worth continuing at goal weight as you transition to maintenance - evidence for muscle preservation is strongest during the deficit-to-maintenance shift, not just during the deficit itself. The reta plus TRT stack covers the main bases for holding lean mass. At goal weight, most people dial back reta dose rather than stopping completely to avoid rebounding while adding muscle.