Genesis once bubbled...
A twinset of HP100s, empty, will have a buoyancy difference from the E130s of one half pound. If you need V-weights for those and not for the E130s then I have to wonder what you're doing, because half a pound isn't enough to make any material difference to anyone I know of.
I don't know for sure about the e-series tanks but the lp tanks are 3-4 pounds more neg (empty) than the the hp tanks. This is per PST and is consistant with the results we get in the water.
As I explained in another post the dealer price list has a set of specs that reads different than the catalog specs. The catalog specs are calculated while the others are measured in salt water and include the valve. Regardless of what the published specs say there is a big buoyancy difference between the lp-104 and the hp-100