Peter wrote:
I am after a simple W&B calculator for a PDA, with a few E6B
calculations (density altitude, say) but nothing else.

I am looking at various candidates that appear to offer a graphical
W&B envelope display:

Aeroplanner
Airplan
Flightcalc
Load Balance
NavigaCE
Niborex
PocketFMS
SA Flightcalc
Teletype GPS
WingX

I recall trying Flightcalc a while ago and it was clearly hard-coded
for 320x240...

Obviously I have written to these firms but one rarely gets a
meaningful reply. I am just trying to avoid spending a whole day
downloading and installing free trial versions

Thank you for any feedback...

I have WingX. It is, by far, the most extensive program out there. But
it does far more than you ask. Most aircraft are already in its
database and it shows weight and balance both in text form and as a
series of points on a graph. I wouldn't have bought it for my 182 where
weight and balance wasn't something I worried about but it comes in
handy for the Bonanza.