[Sachiel7]

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27:1 seems like a little too much of a reduction. Especially if you're running at 40 amps. You can get a good reduction simply with sprockets and chain.
We typically run a drive similar to what you've specified.
We run 1 chip per side, each at a 18:1 sprocket reduction, 40 amps/motor. We use 8" wheels; remember your wheel size will make your speed vary.
If you're gearing down the Chip's 27:1, you will not hit 8 fps, unless you have a large enough wheel. Having a wheel that size will compromise your gearing thus making it pointless.
Also, remember when your worm gear stops motion, your drive wheels won't want to move. In pushing matches or in conflicting forces in your drive, depending upon your worm gear configuration, you may be risking breaking your worm gear assembly. Trust me, I've seen it done. If you want to brake your drive instead of coasting, there are better options than a worm gear.
I'm glad to hear of some rookies trying something other than the drive supplied in the kit.
I would suggest that you shoot for 20:1 at most if you're running at 40 amps. The 12" wheels in the kit should get ok traction, but the 12" size can be a bit of an overkill, unless you're planning on driving up the side of the platform.
Either way, it sound like you guys are off to a good start!