If I have remembered correctly in "Practical Model Railways", either September or October 1983, the late Ron Goult reviewed both Pro-Scales A3 and V2 . In his article he highlighted most of the problems, and also elected to go down the route of soldering the blocks in place. Well worth the read. Steve Barnfield in his much later article on building the V2 mentioned clearance problems with the leading driver, his solution, both with this issue, and the non symmetrical firebox could be of assistance.