Larger radials like the Moki, (I own two) use needle bearings as opposed to bronze bushings in a Saito. The Moki draws its fuel from the carb which goes directly into the crankcase. From the crankcase the oil is dispersed into the intake tubes to feed the cylinders. That's why the Moki can use a leaner gas/oil mix of 50/1. The needle bearings transfer oil better and have less friction resistance.
The fuel mix in the Saito is fed from the carb into a mixing chamber where it is picked up by the intake tubes and then to the cylinders. The Saito depends on blow-by oil from the combustion to lube the internal rod bushings. Hense the Saito must require a richer fuel/oil mix to adequately lubricate the rod bushings.
I hope to soon acquire a Saito 90 cc radial and pair with a Top RC Focke Wulf. (Can't find one until the next shipment - darn covid delays) My personal thought is to purchase the Saito through my local hobby shop and install the prop drive flange upgrade myself to correct the timing issue. The key, IMO, is a careful break in period using a 15/1 mix and pre-lubing the crankcase before the start of each session.
Regards - J Tab