Well, that will make this trickier, but with a few tests I should still be able to figure out everything I need to. Here's the initial test game:
https://www.mediafire.com/download/cdz5mc5wx3zxec0/Test.exeIf you're wondering why I hacked Lemon's Brute mod, it's to make use of the V-align caption (and I'm too lazy to figure out how to do that myself).
I included a mini F jump in the select stage so you can test whether a given computer has the alternate physics. You should probably do the tests on one computer with regular physics (like your own) as a control, and when you get a chance try them out on a computer with alternate physics.
Test 0: You start in a room with 3 warps, each sending you to a different test. Before you do any of those tests, jump around and try to see if your V-align behaves unusually. Does doing a full jump lower your V-align by precisely .1? Is your V-align always between .1 and .5?
Now for the 3 main tests, all trying to determine jump height. Note that apples represent spikes whose heights are multiples of 5 pixels, as references. Each spike is 1 pixel below the previous. Determine the lowest spike you can jump under (for the given type of jump). Note that once you reach this spike, you will only be able to jump under it if you are on an adequately high V-align (remember, higher V-align = lower to the ground), so I'll also need to find out what the transitional V-align is to determine the exact jump height. However, the transitional V-align may be an unstable V-align, in which case don't worry about it for now. Just do tests at V-aligns of both ~.1 and ~.5, and if you only die at ~.1, do more tests to narrow the number down to the specific transition. If you survive at both ~.1 and ~.5, but die to the next spike even at ~.5, that means the transition is at an unstable V-align.
Test 1: This tests 1 frame jump heights. The leftmost spike is at a height of 40 pixels, the rightmost 30. In regular physics, the last you should be able to jump under is the one at 37 pixels, at any stable V-align. The transition is an unstable V-align.
Test 2: This tests jump cancels. The leftmost spike is at a height of 32 pixels, the rightmost 22. If you're able to pull off ideal jump cancels (I'm assuming you're not double canceling), then in regular physics, the last you should be able to jump under is 26 pixels. The transition is at .15. Below that, you will die even at 26.
Test 3: This tests full single jump height. The leftmost spike is at a height of 110 pixels, the rightmost 100. In regular physics, the last you should be able to jump under is the one at 107 pixels, at any stable V-align. The transition is an unstable V-align.
Well, that's that. Hopefully that didn't confuse you.