It turns out Greenlee sells a step-drill which goes all the way out to1-3/8 inch diameter holes which you can buy at Lowes; I bought one and finished drilling the holes in the battery mount. The stock Odyssey mount weights 13.2 ounces; my "lightened" one weighs 9.4 ounces. I'll make one more, as I most likely will go with two batteries. Since this aircraft will be IFR capable and will not have a vacuum system, it seems prudent to have two batteries, one set up to run an "essential bus".
