I keep a close eye on these adaptors, because I HATE trying to fit oversized boards into my backpack. I've not seen the type of adaptor to which you refer.

As an alternative, I've seen a number of 4x4 adaptors to the rounded edge speed graphic board on EBay. You could pick up one of these, and also purchase the 110mm adaptor to the speed graphic board and have an even more compact board than the 4x4.

I've adopted the speed graphic boards as my standard, and the only lens which this board can't accomodate is my huge 360mm f6.8 Symmar-S. A potential problem with the speed graphic boards is that portions of a Copal 3 shutter will extend beyond the boundaries of the board, making them vulnerable in a backpack. As a solution, I use foam rubber in my backpack, and I've increased the size of the hole for these large shutters.