Glad to hear you're liking it Aaron!
I've been wanting to buy some sort of pedal spacer for the ST for quite some time now, but the current offerings were all too thick IMO and would bring the accel pedal too high. Having them all even height might look neat for a picture, but the whole point is to allow better heel/toe usage and with such, you want the gas pedal to sit a bit lower, so they are pretty close to even when you're hard on the brakes.
Anyways, I think Matt's does that very well-- it's only 0.75" thick and moves the pedal slightly "down" and slightly "left" as well. The end result is very good placement I think-- close enough that you can easily heel toe if you want (I really just roll my foot over vs 'heel toe', but same idea) and not too close such that you might accidently hit the gas while braking with big shoes on etc.
On my other car, I bought a replacement pedal that is great for on track, with my track shoes. But if you have boots on, you have to be careful of you'll easily mash both pedals. End result of this spacer is a great compromise IMO.
Anyways, here's some pics. Build quality was great, fitment was spot on, all hardware ware included (2 bolts). By my measurements, the spacer is 0.75" thick, and moves the pedal 0.5" to the left and 0.2" lower. Final comparison pic to start things off