I am very interested in shotgun slug reloading as you can see......
http://thefiringline.com/forums/showthread.php?t=482519
You seem to be the only person I've seen that has found some info about reloading modern sabot style slugs. I am sorry that I cannot help with your question but, I am wanting to know and get advise as well. I took the link to slugsrus.com and I think the components and the roll crimp tool are the real deal. I would think the extreme effort it takes to push the bullet wad combo through the barrel is not a big issue. Upon firing, the pressure when the sabot swells into the rifling is far greater than that when you are pushing it down the barrel. I am not sure about when the wad and bullet leave the muzzle. The sabot should drop away from the bullet when it leaves the barrel and if it is that hard to seat the bullet who knows??