I don't have a Max 35, but I do have a Max 30.

I got it from an estate sale. My Max 30 came with a 0.307" venturi which is larger than the OS stock one for that engine. I also run the engine with the stock strap-on muffler. The engine ran OK but not to my liking. I switched it out to the smaller stock size of 0.275" venturi with stock 4mm spray bar. It runs much better, but with muffler pressure. I also tried it with an open vent, but IMO it runs better w/ muffler pressure. This tells me that the 0.275" may still be a bit too big for good fuel draw if an open vent is used.

The effective throat area of the 0.275" venturi and 4mm spray bar is approx 0.0165".

I run my Max 30 on a SIG Banshee w/ a 9.5-5 MAS prop at around 9,800 rpm on the ground (right at the break point) on 10% nitro and 26% oil (50/50 syn/castor). 

The 0.275" venturi may be fine on the larger Max 35.

Randy's chart is pretty good, but based on experience from the mists of time, I would err on the small side. If you are anywhere near the high end of the range you had better know what you are doing - and when to give up and make it smaller! Trying to use excessive venturis to "Get More Power" was a very common problem back in the day, because you really were power-limited (unlike today). The OS-35S (and the others in the series) came with two venturis, and based on every example I ever saw, the "big" venturi was too big to run with suction. That didn't stop anyone from trying, of course - it was no different from now, every other guy figured he was an expert engine man, and so ended up with burn-down after burn down.

   You are much better off on the small side for the venturi, and if you want to Get More Power, run more nitro. That might also destroy something eventually (like the conrod or crank), but how much are you going to fly a 35S outside the occasional classic contest?

     Brett

He gave two sizes , depending on muffler . Might try a tall one , if its custom .