My capishe has 5 x Futaba 3004. on 6v (i think they were about £6.95 each) Hundreds of flights of extreme abuse (inc. massive elevator flutter twice when the elevator joiner worked loose) and its still A OK. you do not need bigger servos on this plane (i have an irvine 53 screaming its Boll~#ks off)

if i swapped the 3004 servos for digitals the only thing i would notice would be the plane being 2.5 oz heavier. they do not blow back or slow down at all

Dave