Glad to help, Jeffrey. I think you will find lots of crafty people on this forum, and everyone is very helpful.
You could also just buy a low pressure grill. The one TM sells with their "anniversary edition" is presumably low pressure, and can be used with your low pressure tee. Here's an example of a different one sold retail:
http://www.rvqgrill.com/
But I seriously doubt it will be Weber Q quality.
I personally would not store any significant amount (say more than a 1-lb disposable) in the TM. Even that is a bit risky, as the valves on the disposables are cheap. I have had them leak before. And while the valve on a 5-lb tank is way more robust, you still have a heat problem: in my experience, temps inside the TM are routinely at least 10-15 degrees higher than ambient temp when folded in my driveway, and it only gets sun in the morning. That means when it's 85 outside, it's 100 inside. But imagine a 90 degree day when you park your TM in a parking lot where it gets and entire day in full sun. When any gas gets warmer, it expands, and when it runs out of room in the tank, the relief valve will open. Not a good scene.
Plus, you MUST store a portable 5-lb tank in the upright position. If it lays on its side, the liquid phase of the propane blocks the relief valve, preventing its function. So instead of a release of propane when it gets too hot, your TM AND you TV blow to bits. So you'd have to secure it somehow to prevent it from falling over. Not a big deal, I suppose, but still a consideration.
This is why I spent about $150 on a solution to mount the tank outside.
Note that there are 2 major propane tank manufacturers in the U.S.: Worthington and Manchester. Manchester makes a 5-lb version that is simply a mini-version of the all popular 20-lb BBQ tank, which is what is on the front of the TM. Worthington makes a 4.25 lb tank, which is what I have, that has a uniform circumference top to bottom. Unlike the Manchester tank, which has a bottom narrower than the mid-section, the Worthington tank is much less easy to tip over. It is very stable. And with the tank holder I have, more of the tank is gripped as well. The Worthington tanks are much more difficult to find.
Here's a picture that compares the two tanks. Worthington on the left, Manchester on the right.
The fat disposable cylinders are 1-lb, and the portable tanks we are discussing hold 4x-5x that (depending on which one you buy). Obviously, YMMV, but on any given weekend, we use the stove on that tank maybe for 3 meals and the grill for 3 meals, and I am guessing I can go probably 4-5 weekends between fills. Point being: it lasts awhile, and it only costs me about $5 to fill.
Dave