I love this project, the end result is so sweet, so I don't want to bring any negative energy to it. But I have some advice I've said before and imo bears repeating:
I've done aftermarket/custom mods for people for the last decade or more, and what I learned really fast is I never want to take people's money until I have something ready to ship. It's super stressful to have your cash and not have your product ready.
The flip side is it's annoying to deal with flakes who decide they don't want something when the bill comes due. But honestly when that happens I've never found trouble finding another buyer.
That's the seller side. Obviously on the buyer side it's nice to not have your money vanish and then just wait, and wonder. It's better for everyone really.
I would really encourage people to not back projects with cash up front terms. Even bad ass ones like this. Creators/sellers should front the costs of making things. And factor that into your prices, it's okay to make a profit on your time and work. But don't finance things with other people's money, it's just a recipe for stress all around.
(I have a project I've made 14 of, with like a 40 person waiting list. I haven't had time to make more in months. Burnout, getting busy, whatever, I get it. I do want to get to people, but in the meantime nobody has given me a dime, payment has only happened as I've finished them. So me falling off the map for a bit might be aggravating if you were hype to get my product, but nobody is losing anything but a little excitement patience.)