Ah, I didn't realize from your previous thread you were talking about an A2000, not an A500. You can raise the Derringer to fit things underneath it, but then you're going to run into space restrictions with the bottom of the drive sled.
So first, I'd start by ditching the Derringer and replacing it with a "normal" A2000-style accelerator. Since the ones that fit in the processor socket are more rare, you'll probably to get enough $ from selling the Derringer to buy a normal accelerator, and have some left over.
Keeping the Derringer just for the extra ROM socket is pretty pointless, if you use WHDLoad to load your old games you won't need to keep a 1.3 ROM around and you'll have plenty of room for Indivision ECS, Megachip, etc.
Attached are some pics of how those components fit in an A2000. Hope these help!