Works really well, positive comments today at Stanford Hall, bends are made by Walkers exhausts (they make std aftermarket systems) through a local exhaust specialist, trims are just off ebay, search for 3"x5" oval trim, hanger bracket material from B&Q.
Imagination, initiative, a bit of skill and having a lot of cursing available is useful, especially getting the boxes off for the first time.
Not totted up the total price yet, as the design was done as it was built but it is half the price of going to a custom builder. You do need access to burning gear to correct the angle of the std 90 degree bends.
I recommend getting under the car and pulling off one of the boxes, this will point you in the right direction.