Idoubt that any amount of head fins would give you 'more' power as not as much heat is lost through radiation as one would think (Ray might know better but Iseem to recall its only about 20% of all heat generated by a model IC engine is lost through its fins and you are mentioning those on the head only) and the rest via the exhaust and heat soakage elsewhere. But I see that you are angling at the possibility of overheating here.

Overheating is situational, is the engine cowled, are there any amount of fins elsewhere on the engine, what is its untended use (marine engines get by spendidly with no fins at all), and what type of head did you make? A conventional lapped contra piston or an 'O' ring insert type? And out of what material, I believe that aluminium conducts heat far faster than does cast iron.

So there are many variables outside of simply having fins or not.

Ihave two A J Coholic heads on MVVS converted diesels, one with fins and one without and both seem to run just dandy and I consider tall finning like that found on hotter glow engines to be a concession to aesthetics on a diesel more than anything else - fins give definition to the shape of the engine and add 'speed lines' or the impression of motion in that direction.

Many, many tradition old school diesels simply have a screw on jacket with a solid head disk and only fins cut against the liners side and when you consider that the contra piston only has contact to the outside world through its peripheral edges onto the side of the liner then having fins well above that may not help much at all.

Do you have a pic of what the head looks like mate?