You're right Brian...
Check out the posts from rmvpa007 on the link below. He's basically saying that you can use a modified 12a counterweight to balance the assembly and install the front cover without modifying it significantly. I have no clue as the accuracy of his claims though. Surely a custom counterweight could be made to facilitate the front cover issue, or mitigate the risk of grinding through it. Again though, I don't have all these parts in front of me to know what would be possible or not. I do know that the Renesis counterweight is pretty sunk into the front iron...
http://www.rx8club.com/rotary-swaps-...-255013/page8/