I have the same cover on mine and the aluminum pumpkin. I think the aluminum housings are larger than the steel ones. Either that or the IRS cages aren't all welded with the same clearances. I was pretty certain it wasn't going in and tried all the other orientations possible also. I ground a little off the places where it was rubbing while trying to install it and was able to force it through the hole. I used an overhead hoist to pull it up from the bottom which made it a little easier.