Sub-frame connectors... Please build them correctly!

Most of what has been stated in the thread so far is pseudo-engineering. Sorry, it is. The computer "analysis" that was done is next to useless. It doesn't even come close to modeling any of these cars, and makes assumptions that you have no way of justifying. The idea that parallel members don't carry a load is completely false. Take a look at a truss style bridge sometime. If you took out all the parallel members you wouldn't even have a structure anymore. These cars themselves have multiple areas of parallel structural members.

The biggest issue with your "analysis" on non-welded subframe connectors is that you're only testing a single loading point. Obviously, these cars can be loaded from ANY point, and not just with a single input. You'd have to do a full analysis with regard to bending AND twisting, which isn't what you've done. Not to mention the additional structural members, the stiffening effects of the formed sheet metal in the floor, etc.

Welding to the floor isn't necessarily the best way to install frame connectors. Is it as strong? It can be. But keep in mind you're welding together two different thickness's of metal, which creates stress issues. Not to mention that all of those will probably be MIG welded, so you have a somewhat brittle weld connecting a heavy gauge metal to sheet metal, which will still flex, and could cause cracks along the edges of the weld. Not to mention the difficulty in cleaning the chassis and welding the entire length of the connector. If this isn't done on a fully blasted car on a rotisserie, the welding will be less perfect, which will reduce performance.

Welding in a tubular frame connector that doesn't attach to the floor can be just as strong. It does depend on the cross sectional area of the tube, and the thickness of the wall, but it can be equally as strong. It's not a perfect solution either, you can still have stress issues if you're welding a really thick wall tube to the frame, so larger landing plates than most people tend to use would be better. But you can weld them in on a completed car, it's much simpler to weld them in if the car isn't on a rotisserie, and they can be home fabricated. Are the home fabbed one's as strong as they could be? Probably not, because everyone makes compromises. Thinner or thicker wall, smaller cross sectional area to clear certain structures, etc.

I don't think that there's a "BEST" way to do the frame connectors. The laser cut subframe connectors certainly look more factory, and I think they do an excellent job of stiffening the frame. But so do tubular frame connectors, especially if they're done with larger landing plates. Both versions will significantly stiffen the car, which I can attest to since I have actually installed a set of tubular frame connectors on my Duster. The difference is night and day.

The "best" way to add a subframe connector is the way that you're set up to do it. If the car is on a rotisserie and has been blasted and cleaned and you want to retain a factory look, the laser cut connectors are the way to go. If you're doing this at home on a completed car, don't have access to a rotisserie, or aren't skilled in welding heavy gauge metal to sheet metal, the laser cut connectors probably aren't the best for you. Same if you're racing, because a lot of sanctioning bodies will put you in a different class if your connectors are welded to the floor. You can build tubular frame connectors that will work just as well or better than the laser cut ones, it just depends on how you do it.

You can build a tubular frame connector that is stronger than the weld to the floor kind. And even the weld to the floor design can probably be made stronger than the US Cartool ones that everyone uses. But you'd have to do a structural analysis on the entire chassis to know which one was actually better, and NO ONE has done that. Bottom line is, either method is light years better than doing nothing. And unless you're racing the car on the track or road, either method will more than suffice. And if you are seriously racing your car on the track or road, then you'll probably need a full cage anyway, and the method of installation will be dictated by the sanctioning body you race with, so that will be your deciding factor.

And yes, I do hold an engineering degree. I have a bachelor's in Aerospace engineering, with my major focus being in structures, although that's not what I do for a living. My take on subframe connectors is here http://www.forabodiesonly.com/mopar/showpost.php?p=1970045503&postcount=39. And I fully admit this is not the absolute "best" or "strongest" way to make a set. But it accomplished what I wanted to accomplish, and I can tell you the result is a car that is significantly stiffer than it used to be. I also have a set of US Cartool connectors for another one of my projects.