I might be wrong on this, but, if you're going Durso/Stockman (Stoffman? I never remember the names...
ops: ) don't you want the standpipe to be larger than your bulkhead (just using a bushing at the join)? So if you're bulkhead is 1.5" I think you want a 2" standpipe despite that you will likely be going with a smaller diameter pipe down to your sump below the bulkhead.
2" is huge though. I can only imagine what that monster would look like (make sure you have enough clearance in your overflow if that's the size you end up using!)