Hi Bob,
Thanks for the update. Good to know you have now got things running properly by powering your Aircrew from your aircraft 12 volt supply (suitably switched and fused I trust).
The Raspberry Pi's used in PAW (Classic or Rosetta) are both generally fine with their designed power draws (including USB to RS232 converters and the 'extra' WiFi for iGRID, as these have all been tested in development. As we have discussed before, adding any additional loads can be asking for trouble (especially if anything goes wrong - such as an SDR or GPS developing a fault).
Remember that when James compiled the Aircrew Manual, he would have been working with a 'bare' PAW without USB to RS232 or iGRID, so it would be perfectly capable 'power wise' of supporting the Aircrew in that state. In a similar vein, that's why we always recommend powering PAW from its own dedicated supply - i.e. not 'sharing' a 2-port USB adaptor - especially with a power-hungry 'flat' tablet or phone. As you are of course now aware, connecting the Aircrew to the PAW by USB (rather than WiFi) also prevents display of aircraft Reg ID as I reported previously, so swapping it to an external supply with WiFi connection to your PAW automatically resolves that issue.
Good result!
Best Regards
Peter