Ok, I have a n82 pro and a Foxx Hybrid (very much like your KingTuk, Crossbreed, whatever). I carry a G26, so a bit heavier and bulkier than your shield. Here's my .02 on the holsters.
When I first got my n82 I hated it. It felt like it was sliding down my backside all of the time and just wasn't all that comfortable. It printed more than I liked and it felt stiff with the polycarbonate mold for the gun. Enter the Foxx hybrid, I thought that dual clips and spreading the weight out over my belt would help keep my pants up, nope it didn't at all.
I labored on with the Foxx though, it concealed really well and I started trying different carry positions, about 4:30 is what ended up working for me to keep my pants up. The bottom of the holster catches the top of my right butt cheek. This was alright until the summer started and the temperature started to climb. When I get sweaty the polymer handle of my G26 irritated my skin and it's too damned hot for an undershirt. I would have a rash for literally an hour after taking the holster off from the grip and while it was holstered it was rather uncomfortable to say the least.
So I decided I'd try the n82 again, it covers the handle so no part of the gun is touching my skin. I moved it back to 4:30 and I noticed my pants weren't falling down anymore, in fact, my pants were staying in place better than with the Foxx. Strange... So I kept carrying, as I sweated the holster really molded to my body quickly and it become super comfy. The only issue was that the polycarbonate is thicker than kydex and it is off of the gun a bit adding even more thickness (the only place that really touches the gun is the trigger guard) so my beltman belt was just too tight when sitting (and I spend most of my day sitting). My wilderness belts always sucked for me so I picked up a Volund Gearworks Atlas Cobra belt and bam it was perfect.
So now my ideal carry system is my Volund belt with my n82 at 4:30. The print is about the same as with the Foxx in that position and I can wear it all day, hot, cold, sitting, standing, walking, running in total comfort. I do notice the gun is there, but it's not at all uncomfortable.
Part of the issue with the KingTuk IMO is the smooth back to it. There is nothing to grip and this is the same of unlined Kydex. It will slip if your belt isn't tight (yes I did have an all kydex holster so real world experience). The N82 uses suede on the back which does grip like rough-out leather but is softer on the skin.
Yes, I can get a full firing grip on the gun on the draw. It does take some getting use to shoving your thumb inbetween the grip and the holster and that lil twist takes some getting use to as well. However with some dry fire practice you can get it down to where you're just as fast as coming out of a kydex holster.
The glock is still heavy, there is no changing that, and your shield is the same way, you can't change the weight of the gun (well a bit with lighter rounds), it is what it is. I'm looking for a lighter weight gun right now anyways, but haven't found one with the reputation of the Glock reliability, but that's a story for a different day. When I do pick a lighter gun I'll pick up a N82 for it too. IWB isn't as comfy as OWB, but with a set up that works for you it can get really damn close.
For your reference, I'm 6'0 / 215 with some love handles.