On Tuesday, 17 May 2016 03:19:08 UTC+2, Mark628CA wrote:
I just installed an LX-Nav S80 and remote stick controller, and while I am
mostly impressed with the hardware, the operating manual is sorely lacking
in many areas.

I found the German manual had a little bit more information in it than the English one and Google Translate worked well enough to make sense of it.
Also the merged S8*/S10* manual is a bit confusing so I use the previous S80 manual (LXS80ManualEnglishVer0501i.pdf).
They really could spend more time on their manuals.

When trying to enter the value for ballast weight, you have a choice between
overload, weight, lb/sqft and kg/m2.

I prefer to work with weight. One litre of water = one kg so that makes entering the ballast easy for us metric folk.

Absolutely no explanation is given in the manual about how to use these
numbers. I can understand lb/sq ft and kg/m2, but this isn't how I normally
load my glider. And I have no idea what "overload" might refer to.

Did you read page 66 of the S8x/S10x manual or page 52 of the S80 manual?
It explains the fields and how the overload is calculated.

▼▼▼▼▼▼▼▼▼▼▼▼
Reference load (wing loading) value represents the value at which the polar was
measured.

Reference weight corresponds to the weight value at which the polar was measured.

Maximum takeoff .weight is the maximum take-off weight allowed for the glider. It is not used in the calculation; it is just a reminder to the pilot of the maximum take-off weight.

Empty weight is weight of the glider without the pilot and ballast.

Pilot weight is the weight of the pilot with parachute and baggage.

Co Pilot Weight is the weight of the co-pilot with parachute and baggage.

overload = (Empty glider weight + Pilot weight + Water ballast) / Minimum glider weight
▲▲▲▲▲▲▲▲▲▲▲▲

The "minimum glider weight" referred to in the overload calculation above is actually the polar reference mass and not the empty weight. That is very misleading wording.

I just want to set my empty glider weight and pilot weight with chute in the
appropriate fields and then enter the weight of the ballast I intend to
carry.

You just need to add your parachute weight to your own pilot weight and enter the figure in the "Pilot weight" field.

If you plan to use your S80 with XCSoar then please take note that the way XCSoar and LXNav determine the overload factor is different and not entirely compatible with each other however there are work arounds.
I find the way LXNav calculate the overload factor to be less intuitive than the way XCSoar does it.
I posted it in the XCSoar forum in case anyone is interested https://forum.xcsoar.org/viewtopic.php?f=19&t=2564