Kirstey,
If it is properly/accurately calibrated then all well and fine and I really hope he enjoys using it.
If it is inadvertently calibrated to under-read, ie 10alpha is really 14alpha then it if he relies on it too much it is inherently very bloody dangerous.
Likewise if it over-reads, it probably won't be helping him at all and will merely be a useless distraction that may not enable him to get the best out of the aeroplane.
Off to my hangar to fit aircon and a dehumidifier to my Aeronca Super Chief. I'll then call it it Stik's Super-Cool and Dry Chief and will accept the 300% increase in runway required.
I'm sure that Mr Aeronca would have installed them as standard if he'd had more money to splash about!
Gotta go, the hangar beckons.
Stik