Ken,
You hit the nail on the head. At low frequencies, at VHF and down, I wouldn't worry about picosecond delays or femto-farad fringing C's. And I bet 99% of the Nano users will be looking at SWR only............no worries about the measurement plane.
I am mounting my Nano on a plate and adding N connectors with short cables connected to the plate to strain relief the Nano's connectors. This will give it a little more mass to deal with even the tugging of the USB cable:)
73
