The claim of 120MPH + is completely legitimate.
Weather permitting, on summer Thursday evenings , the Union Model Airplane Club met and typically there were 5 circles flying. Larry and several of us would go to the furthest away circle . It was 1966 and 1967.He was conducting development/ testing of the Super Satan design for Carl Goldberg and his LS Tuned Fox 36xBB line of custom tuned engines for retail.
We timed from outside the circle during flights (sans streamer) and he would always time himself as well. Real 120MPH + flights occured.
Larry had " graduated" from Fox Blast. A club member and pharmacist , Al Needleman, mixed his fuel for a long while. Binky pacifier, small hub Tornado Yellow 8X8( boiled & balanced), prop hub and drive washer modified to prevent blade toss. There were more LS tricks to achieve speed, but I was only a teen and most of us weren't privy to that info.
Engines were custom re-worked by Larry- I still have a few . (Someday I'll sell them since I primarily fly electric now since returning to Ukie).
I built and flew a Super Satan in 1967. It was ridiculously fast . So much so that it was too much to comfortably compete with. Larry twanged my Satan one evening and that was my one and only.
I used Voodoos , some stock, some modified with longer booms and scratch built some to save weight. Won Senior combat in '69 with a Voodoo and an LS Tuned Fox 36xBB. Also liked Sneekers and Demons.All were great designs ,but not terribly fast.
Another club member at that time, Mike Luciano, built a number of Satans and achieved nearly similar results.
I have no reason to make any of this up. Larry knew his engines and custom reworked motors for many, many people .