[Alan Douglas]

Removing the 83 reduces the power-transformer load by 15 watts, which has to be a good thing.  There may be some differences in Gm readings, but no Hickok is a laboratory instrument.  Once you get used to your particular tester's quirks, you're fine.

There's no problem running an 83 on its side. The plate voltage is just 150V, and it's only applied when you push the Gm button. The 83 has plenty of time to warm up.