Oh... i remember to the demos, we did many demoshows in the 90s, so i know which demo has timing issue (or any hw related issue). i prepared basically for every year with a period correct config - but it does not mean, i will run them on the “closest” hw. I switch hw, if it is too slow, or has some issue.
dx4 100 vlb 94
Socket5 p120 95 (ca 2x faster)
Socket7 p233mmx 97 (ca 4-5x faster)
K6-3 450 99 (ca 8x faster)
P3 1000 2000 (12x faster)
I recommend to you, run on a period correct pc first (mostly they are slow - 10-20fps was normal). The normal gus classic also important, the guspnp plays sometimes differently, with different speed, and the demo is timed to the music. The late demos support directly the interwave.
Another issue can be, the gus is sensitive to the isa bus timing. I dont have too good experience with the last 3.74, it works well in a fast 486, but the it does stupidity in an mmx or faster computer. I dont remember to the same issue with the 3.4.
The hardest part is with the datapath the special modex modes - some demo has 4-5 switches, it is impossible to set it pixel perfect for the whole demo.