The firmware already checks if it's on a 2.4 or 2.5 and selects the overlay size appropriately, so maybe that logic could reallocate some of that overlay to firmware: The official firmware still sticks to the 370 LEB limit but a comment in the genimage.cfg file says "If you're building an unofficial firmware and you don't want to maintain TPi2.4 compatibility, you can uncomment this other line to use the TPi2.5's higher limit."