That design has been around and in use for quite somw time now. I think its actually a BK motor mount part that he sells as his own. I havent owned one myself, but I have seen a few in use and they appear to do OK.
I can't decide if its more fun
to make it...
or break it...
knotted, FD has been selling those for sometime, I actually have a set that I've used on my Savy for quite sometime now with no issues. Rather than using the "block" mounts, I simply dropped my original motor plate down by about 3/16 of an inch and mounted the rings directly to it using the stock motor mount holes for adjustment, it actually worked great.