Or would be better to use a center fed inverted V with its low
impedance that can be mathed with smaller losses to 50 Ohms?

Pass go and collect $200.... Way better than any other
method...Scrap the tuner...Thats the last thing you want
for QRP...Center feed with coax...Can be lightweight rg-58...
You really don't even need a balun...In the unlikely event rf
at the rig is a problem, just roll a few turns of coax at the feed,
and tie wrap it...As a bonus, you can add wire, or insulators,
and use for other bands, or make it multiband, with insulators,
and jumpers to change bands...No tuner needed anywhere,
once it's set up. You could make one for all bands...
Would look kinda like this for a 20-40-80m version.....
-----------------o---------o-------00--------o----------o-----------------
You jumper all the insulators for 80..Only the inner ones for 40,
and none for 20...In that pix, you can't see the jumpers.....
Can be wires with gator clips, or whatever....I've used that
portable many times...Usually built on site from wire and stuff
I carry...But I usually just make them for 80/40....
MK