Michigander:
I believe the R8 was the same gun as the HW50s at some point? I also know the HW50s goes by HW99 in the UK.
The jointed cocking linkage that you mention is still present on the current HW50s guns. I kinda have a theory that that feature is a big reason why the gun is such a stable and consistent performer. The jointed cocking linkage allows the slot under the forearm to be much shorter, which in turn allows the screw(s) fixing the front of the action to the stock to be under the forearm instead of the two normal screws on either side of the stock forks. I personally think that the screws that hold the gun through the stock forks are a big reason why guys have trouble with inconsistencies in springers. If you look at a springer stock without the action, the stock forks look just like a tuning fork. I feel like that allows the vibrations of the shooting of the gun to create some kind of resonance that makes the screws loosen. That's where you get the star washers, and the blue loktite, and the other band-aids like steel posts to bottom out the screws on. All of that is to combat the fact that the side screws through the forks simply won't stay tight. You've also got the possibility of those thin wood pieces of the fork contracting and expanding with temp and humidity levels. My HW50s never needs the screws to be tightened-they never loosen. I think it has to do with only having two screws holding the action to the stock, both of which are on the bottom of the gun and none of which are through the vibration-prone fork of the stock. Just my thoughts, based on personal experience.
About your winter project of turning an HW30s into a 10m gun.....it's always nice to have a gun project to keep a guy busy. The 50s is probably a little more power than most people think of when considering 10m shooting, although you could tune it down, but that could in turn make it a little tougher to shoot due to longer "lock time." For indoor, cold-weather, 10m type shooting, I'd highly recommend going with a dedicated 10m gun like the FWB300s instead. I had mine out yesterday for the first time in quite a while and just marveling at how well those stocks fit the shooter, how amazing the trigger is, and generally what a cool gun they are. Looks like they're going for about $495 these days, at least for the rougher looking ones. Then you can redo the stock for your winter project.
As far as chopping the barrel, I'd move forward cautiously with that idea. I've read on the forums where a bunch of guys have chopped HW barrels and still had good accuracy. I sure wouldnt do it to this one though. The reason being, the barrel is slightly over-sized. Any pellets other than the hard boxed Crosman Premier almost fall through, until they hit the choke. If I cut the choke off this one, pellets pushed through the barrel wouldn't have any resistance. If I understand it correctly, a little resistance is necessary in a springer or the piston slams into the front end of the compression chamber, ruining piston seals. So, maybe push a pellet through the bore of whatever gun you're thinking about chopping the barrel on, just to make sure the only resistance isn't from the choke. The flip side of that, if you've got a loose bore but have a way to rechoke after the chop, than go for it. Cocking effort will go up with shorter barrel though, so keep that in mind.
picking the best group. I thought it was a ten shot group but I can only find nine holes. It's no PCP group, but from sitting on a bumbag, quite pleased with it. Center to center is just a hair over 1 inch. This gun can usually shoot groups at 55 yards that are 1.25-1.5inches, so this is a little better than the norm. 
