I have 2 saito 4 st formationrokes and 2 magnum, 2 strokes all of which require some nitro to run well. I initially ran my first magnum on FAI but it struggled to maintain a stable idle, similarly my first saito I started off with 5% nitro but it definitely runs better on 15%.

In addition caster oil is not recommended for the saito four strokes due to carbon deposit and saito recommend full synthetic oil. I am sure there are many people who have run saito and other 4 strokes well without nitro - just that the manufacturers don't recommend it!

My two stokes I run a mix of castor and synthetic (9% each) am 10% Nitro.

What engine do you have for yours? Is it nearly finished yet?