Yeah test running the engines on a test stand is a good way to try the engines out at first. This lets you have access to all of the adjustments easily. Plus it is easy to see things like the fuel tank, etc.

I tend to suspect that the engines have a bit too much compression for higher nitro glow fuels. I typically run 5% nitro glow fuel in all of my engines. I only go with 15% or 20% nitro glow fuel when the engine runs poorly otherwise. My first Saito that was picky with glow fuel is a .80 and it really preferred zero nitro glow fuel. I had to run it for a long time with no nitro glow fuel to get it worn out some before it would use 5%.

I test ran my Saito 1.50 using 5% and it worked OK for me like that. I never tried higher nitro content fuel with it since it ran Ok like that.

I would double check the cam timing on the engines. It is pretty easy to get the cam out of time with the engines. The angle cut gear teeth make it a bit tricky to set the timing. So if someone isn't paying attention it could be off.

I sometimes wonder if Saito made their engines for two different markets. The USA market with lower compression for more nitro in the glow fuel. And the rest of the world with higher compression for no nitro glow fuel. Thus if you got a engine not made for the USA market, you would have problems using nitro content glow fuel in it.