Hi Cdncoldwater,
I think you are missing the point of a PAD Tech 40 (and even solo training). With PADI Tech 40 you may perform the training in a recreational single tank rig as long as you have D-rings available to secure your stage bottle. You will be taught to attach your stage bottle in the water (you don't have to pack the stage bottle on deck and hurt your back). U/w you won't even know the stage bottle is there. It is almost weightless.
Solo training makes you think about redundancy and taking care of your own bad self. A good solo diver can be the best dive buddy you can ever have, because they don't need to rely on you for most u/w safety issues. You will be your buddy's escort while he/she performs their direct accent to the surface in case they suffer an u/w issue.
You also get a formal primmer on gas planning and you learn to gauge/calculate your SAC (some call it RMV—PADI taught me to call it SAC).
The Tech 40 class is a comprehensive course like no other you have had in recreational diving. Also, you learn to be a real dive buddy, a true dive buddy. Not a faux buddy like in OW. You will plan a dive and then as a team you will dive the plan without using computers. You will learn about staged decompression for real. You will learn about deco gases.
My buddy team was given tasks. My buddy and I divided up the tasks and followed our dive plan. We were busy. Yes, we were task loaded. We followed our decompression schedule no matter what. It was rainy, windy, and cold on the surface. It was cold and murky u/w. Did not matter, we had to follow our dive plan.
To some degree Solo, and especially Tech 40 adds additional layers of discipline to your diving. With those two classes, I feel I have the background to handle almost all contingencies u/w from 0 to 130 fsw for my buddy and I, or if solo.
Am I a practicing or real Tech diver? Heck NO!
Tech 40 and Solo training were the only classes outside of OW, that were worthwhile for me.
cheers,
m