Keith,
While I have not weighed the completed unit, I do not think there will be an issue with the neck of the bottle carrying the weight.
I can weigh it tomorrow if you like. Weight is 1.75lbs

The slimline unit was $40.00 bucks which included the nicely machined metal cap and standoff, tubing, clunk, self sealing fueling probe,fuel jug and a hand pump. The pump is the Sig Gazzer $35.00 and the 5 gal jug was $7.00 bucks at Lowes. The box and switch came from radio shack for about $10.00, two filters $5.00 each and the 6 cell Nicad pack $2795.00 came with my P-70.

One of the reasons I went this way was to have a mobile fueler. Since I only fly a P-70 a 2.5 gallon container will provide me with 5-6 flights at the local flying field so I don't have to carry as large of a fuel container on those days. Then when I go to a multi day meet I can simply move the pump system to the big container. Also it would allow you to transport a fuel system in say a jetcase and then you can stop by Lowes and pickup fuel jug at your destination.