I'm quite stumped. I can't seem to figure out how to create double tap logic.

I'd use flags. Flags can be either on or off. When you press the button, turn a flag on. Then compare if the flag is on and within a certain time limit if the button is pressed again, otherwise turn the flag off.

Since the conditions are read pretty quickly they might be instantly switching the flag then checking for the second press while it's still the first press. Try switching the order of the conditions around.

Can't you just select "Double click" when setting up the Click event?

Is there a double click option there? I haven't used Fusion in awhile. At least I don't remember it being a feature of MMF2

Yeah, after you click "User Clicks" (whichever version), under "what kind of click", you select "Double click".

It's in CF2.5 and MMF2...