Hey look! v82slo and I have the same kind of flooring. Thanks for your response earlier, by the way. It encouraged me to try.
It's funny. I rent out a room to an accountant friend. It seems that every day he walks through the front door, he finds me sitting at the kitchen table with a rifle & welding mask or cutting metal (sparks flying everywhere). I can only image what's going through his head.
I have the G&P short, jungle, non-RIS launcher and a standard SR-16. The M203 did not have notches for the chamber fins. I definitely took my time, making sure that I didn't cut anything I didn't have to. I wish I had taken pictures a long the way to help out anyone else stumbling onto this thread in the future. But it's together now and I used locktite on the front two remaining RIS screws, so I'm not rushing to disassemble it for pictures. All I can tell you is that it's not really a big deal and it is completely doable. Here is a pic of the finished project:
