It's not the trigger, or the shape of the stick that matters for Tron. It's the restrictor. The right setup ONLY came on Tron sticks. Not Xenophobe, Not Discs of Tron, Not Gorf, etc. The deal is that the stick is ALMOST a 4-way, but not quite. The result is that you CAN hit the diagonals during the non-lightcycle stages, but you WONT hit them during the lightcycles, unless you try (and then you'll die).
The best thing is to get a true Tron stick, but those cost $$. If you don't want to pay for one, there are still two ways to play Tron without the lightcycle zig-zag problem:
If your panel has an 8-way and a 4-way, you can use the 4-way during the lightcycles. You can use a button in place of the trigger. Or you can rig up a 4-way top-fire, or even a 4-way trigger stick.
Or, (and here's what I'd do)- if you're building specifically for Tron, but don't want more than one stick on the panel, and don't want to spring for a true Tron stick, buy one of RandyT's Top-Fire Prodigy sticks from
www.groovygamegear.com. Play in 8-way mode for everything but the lightcycles, and then switch to 4-way for that wave only. The top-fire is almost the same as the trigger and is useful in other games, you don't have to change sticks during play, you don't have to clutter up your panel, you don't have to sell your firstborn for a real Tron stick, and you've got the whole 4-way game problem solved to boot.