I knew you were going to ask that. Unfortunately I can't help ya. My Dive Rite BPW setup is in California and I'm in Idaho. I have my Transpac with me but that doesn't help you any.
I have the old 30-lbs Venture, the old 40-lbs Venture and the newish 40-lbs Venture 360. The old 40-lbs Venture came with my Transpac which I bought first, the 360 came with the BPW and Transplate harness. Then I found an LDS that had old stock 30-lbs Venture wing. I switched & swapped all these things out between the Transpac and Transplate to make sure that they all fit & worked. The BPW and STA (or SMP as in Dive Rite parlance) were bought in January of 2009. I don't know if DR had changed the dimensions since then or even before then.
As far as tropical diving goes, I have yet to do any so I can't tell. However, for temperate diving in California, I noticed that the 30-pounder vents easier than the 40-pounder. Can't really tell the difference in performance (i.e. more or less drag, affects the trim differently, etc.) other than easier venting with the 30-pounder.
I do use the 40-pounder when I go scallop/snails harvesting because these bad boys are heavy as heck and I don't want to carry a lift bag.
good info on the 30lb vs 40lb.
thanks