My technique for the last 20 years or so has been to use a standpipe
and fill both wings simultaneously, vacuuming first especially if the
bags are not vented. This worked for the LS-4 (both vented and
unvented bags), LS-6 (unvented), AS-W20 (vented), another AS-W27
(vented), but of course not the Nimbus 3. Never flew with water in the
AS-W17 or AS-H26.
The funnel sounds a bit 70s. I don't like to support one wing full
of water on a wing stand either, as I've seen people squash the foam
core that way.
This set of bags doesn't vacuum as well as others. Perhaps they just
need removing/replacing using the correct facial expressions and
abusive phrases? Would it help to drill more holes in the inner pipes?
The factory bags are vented and fill easily, but look like water bed
material. After having a similar bag break in flight - filling the
cockpit with water - there's a preference to use heavy duty bags. At
least the factory bags are not shower curtains as removed from the 4
and the 17!
Somebody may know how to vent the Smileys...
Jim