I just had a set of the Rikon guides shipped to me from Highland wood working in the US. The delivery via FedEx was quicker than most UK deliveries from a UK supplier.
The top guides installation was straightforward, initially did not pickup on shortening the blade guard, wondering why I had lost 4 inches of cutting capacity.
When I tightened the lower guides to the L bracket, the guides are no longer sitting square. The frame looks ok. And I would have said the bracket was square. Might just shim one edge to kick it upright.