Did Ranch Fairy change his name and come back on here?
LOL, I was just going to comment something very similar.
I'm in the same boat as most here, I've been shooting HIT's in multiple 4 & 5mm arrows for over 10 years and have had zero issues with breaking heads or smashing arrows.
If you're worried about the integrity then go with the IW system, but threads are not getting stripped and having your threads bottomed out actually make the system more rigid and will cause the head to snap off right where the thread and the insert meet because there is no room to bend, having the shank of the head above the insert and threads allows room for a little bit of bending or give which is actually more durable than something that will just break off. Several broadhead manufacturers use softer steel on their threads than the ferrule for this exact reason.
HIT's are no different than any other insert out there, all of the inserts have threads deeper than the threads on a broadhead or Field Point. A bolt/thread is designed to clamp the head down to the shaft and that is why the bottom of the ferrules are squared and the end of the threads are not. If your shaft is square and your head is tight against that square surface then there should be zero give-on impact, unsquare arrows cause broken ferrules.
If you're having to rotate your inserts to get them to spin true your arrows are not square because if your arrows are truly square then all the rotating in the world won't make them spin any different. Only an untrue arrow will change on rotation. The only reason to rotate your broadhead on a square arrow is to align it with the vanes or if you're really picky the spine of the arrow, which neither of those things makes a difference for 99% of archers.
Valkyrie makes a center pin system if you really don't want to deal with threads.
You must really go through a lot of targets because even though I hunt for food, I shoot thousands of arrows a year through my bows and wear out a lot of targets and I only shoot broadheads for a couple of weeks leading up to hunting season. I personally think shooting the exact arrows and broadheads your hunting with far outweighs any minimal gain in strength from hot melting your broadhead and insert in together.