Cant comment on smiths in central or eastern Canada,but here out west would recommend Dave at Cape Guns.Ive had work done by him and was very happy with the results.Hes also involved in IPSC and understands what a open shooter requires in a gun.
Other option(possibly cheaper and quicker),would be to buy an open gun from STI(freedom ventures),shoot it a bit and then do the final tweaking as necessary.
Open guns are always popping up on the EE here,some at really good prices as well.