Well, I appreciate the interest and opinions. To satisfy everyones curiosity, here are further explanations;
A turning driveshaft is larger than a stationary one at the points where the U-joint yokes are located. You can orient the DS so the yolk either clears or hits something adjacent to the DS.
That something is the header. The Borla is one-piece, so there is no downpipe seperate from the header. Were it that simple, I could pull the downpipe and have it modified fairly simply. The contact has dented the header and in addition to the self-clearencing it places stress on the entire unit, which I suspect may eventually damage it further upstream.
Banks header will not fit, despite all the advice on this forum. Borla does well, but is no longer made. Other companies, at the time of install, were either unresponsive or unwilling to state whether thier product would fit the renix. So my takeaway assumption at this point is that there are no quality headers available for renix 4.0. I may be wrong, but that was the case several years ago. Either way, I dont want to intentionally ruin the header assy.
If the front DS turns, as it does on a solid axle, and I get any straight compression on the front suspension, there is a large crunch from the DS mashing the header pipe. I can live with that temporarily when in 4wd and going slowly, but not everyday speedbumps and cattleguards at 50 mph.
The posi-lock is NOT the bombproof solution you think it is, as I stated in the OP. At $200 for the part and $300 for install, it never worked. The company tried to distance themselves from the problem by blaming the installer, and the installer blamed the company. I dont want to throw good money after bad, so I pulled it out.
I know this subject is a bit of a nerve, I suspect because it may be a shibolith. Everyone just Knows the CAD is bad, it just is. And anyone that questions that "fact" must be a heretic. I've had it not work a couple times, mostly hose issues. Local advice says the switch sometimes fails, and rarely a fork. Well, Ive had the posi-lock fail twice and never work correctly. Does that make it junk? Most people think not. It may work fine for some folks, but failed me and the prospect for success in my case isnt worth the expense. I wanted peace of mind and I will never have it, even if they fixed it today. The difference is that I can fix the vacume system easily in the field. I cant fix the cable (but could jam it over if necessary) and cant fix a broken header.
From a system engineering standpoint, I understand that a vacume system is inherently less reliable than a solid axle. Its another entire system to install and maintain, vacume. But I dont see folks complaining about ARB lockers. It requires an entirely seperate system to purchase, install and maintain in order to operate the locker. And it has a known track record of failures. But yet, everyone clamors to buy it and sing its praises. From a systems standpoint, it is not much different from a vacume operated CAD, except that it is way more expensive and complicated. But we just KNOW its good. Shiboliths.
I would prefer to purchase a new D44, HP, trussed front end. But thats not in the cards. The vacume can work, it is cheap, and as reliable (or more so) as an ARB locker system. It is not the gold-plated, bomb-proof solution. But parts are inexpensive and easy to maintain. All I would like is to make sure the "system" is as reliable as possible by addressing the known weak spots, and keeping up with regular maintenence.