[VAC] Variable resistor for brake controller?

[Robert C Townsend <rctowns@xxxxxxxxxxxxx>]

The K-H installation pages Harvey B. so graciously shared with a couple of
us (back-channel) make reference to a 'variable resistor' ('not supplied')
for 'trimming' the voltage to the trailer brakes - I'm thinking that this
would be a GREAT idea, especially when one is using the same puller with
different trailers...

Any electrical engineers (nudge-nudge, Dr. J) out there have a suggestion?
I'm thinking an ordinary potentiometer from RadioShack - but would like an
informed opinion as to the range/type/values for this application...

Tuna
(who is putting that K-H brake controller into the Durango, and taking it on
a test run down to Tucson to pick up a 12', 1983 'Burro' TT that's going to
be painted purple, to match the Prowler... which will be the Burro's
'puller' - putting the Jordan Ultima 2020 into the Prowler...)