say you oversized it by 1/2 hp , what might that do ....
As long as the TXV (or the cap tube) is properly sized for the condensing unit capacity there should be no problem going up one size. It'll run a slightly lower evap temp and be able to hold a lower box temp. Supermarket cases do this all the time with essentially the same case for either frozen foods or ice cream. the ice cream just requires a bigger unit to hold the lower temps.
Actually, in PHM's case, the 2 HP unit may be the prudent approach. I found some old literature for a couple of other 3-door display freezers which called for 2 HP units.