One must be really careful with any geared engine not to allow the propellor to drive the engine, i.e. maintain positive manifold pressure and enough blade angle to always load the engine, on big radials this is really important as it gets serious expensive very quickly if you miss handle them !!
R1820 on final 1800 rpm 20 inches, forget the fine pitch bit close the throttle as you flare and the propellor comes back to fine as the power comes off during the roll out.
Even the non geared R985 Pratt is same , don't let the prop drive the engine, the counter weights get really unhappy.
Round engines require finesse, absolutely reliable if you treat them well.
Geared Continental is similar hold coarse until the round out power reduction.