I have used these on several planes. DIY and flitetest. Most recently i purchased these for my own design of a b-25 which uses 4x 1806 size motors. The hole spacing is perfect, no mod's needed. Just glue and tape to the foamboard for a solid connection. Here is the build i used them on:
http://forum.flitetest.com/showthread.php?20801-B-24-DTFB-design-and-build-log

This is an extremely accurate convienvce forthescratch builder. For those who'd dream and scheme but do not have the luxury of Dremels or drill presses and scroll saws, this product takes all the guesswork out of tis part of your project. This is one of numerous innovations this creative team has come out with. Thanks guys!

Great Item, quick and easy with perfect fit, take glue great. Sure you could make your own with a 3D printer or make them by hand, But for the price these can't be beat! Besides if you order them from Flite test, the firewalls are going to fit right out of the box the first time and you will be supporting the Flite Test experiance!