That sounds like a typical "20 pound" tank. That designation is the propane weight capacity, so the Manchester 11 lb (11#) tank (or "cylinder") will hold 11 pounds of propane when properly filled (which means allowing space for vapour).
The tank should have its empty (or "tare") weight stamped into it (not just printed on a label), and steel tanks are about as heavy empty as the propane which can be put in them, so the "11 lb" tank (tare weight 14 lb in the Manchester table) should weigh (tank+propane) about 25 lbs when filled.
Depending on vintage (old) and source, some tanks have a "water weight" or "water capacity" stamped on them, which is the weight of water which would fill them... it's an indication of the volume, not the tank weight and not (directly) the propane capacity.
Thanks. That info helps.
I went to RV World and they have the jumbo rigs so they didn't help with the tall skinny ones but said that the price is so high for the smaller footprint tanks ($70) because they just don't sell many compared to the hundreds of thousands of larger footprint tanks.
Also, I asked them about the composite/fiber tanks and they never heard of them! But they said that any ( fiber or steel) tank could explode if forced-filled beyond the safety limits.
I went to Northern Tool and they had just what I was looking for in an 11# tank with the small footprint and taller profile. Only $46.00.
My new tank will sit down in the front V nestled between the 4" high tongue frame. I have a plate across the bottom for the tank foot. This makes the height less apparent and more stable to secure (somehow I'll have to figue out how to "tie" it down.).
Well, thanks again for your, and others', contributions.
Seems that others are having tank questions and/or solutions, too.
Oh, yes. One more thing. I found out that in a pintch one can buy an adaptor to use those small propane disposable tanks (for lanterns, etc.) if you run out of the big tank while camping! And, conversely, you can fill those disposable tanks with your big one!
Done. Over & out.