I've been wondering about these pistols for a while now and if Ruger engineers follow their usual path, the uppers on both the 9 and 40 should be interchangable. Has anyone who owns them both tried a swap? The reason I ask is that eventually, there will be SR's that were confiscated for one reason or another and sold to scrappers. This would put guns into the parts stream and with knowledge of parts interchangability, one gun could become two. I'm counting on the SR series being what the P series was with the SR9 and SR40 being the first two of other calibers.