Thanks for your input, appreciated - I have been thinking on those lines of a substitute Vreg and I do have a Turnigy 5amp BEC, but is a little bulky.
At the moment I am replacing the on-board step-down MP1593 which is kaput with an MP2307 and juggling with the 2 FB resisters that determine the output voltage ( R2/R3 type 0402) awaiting them from RS - these are only 1mm x0.5mm bloody micro surgery soldering. If I can get 5-5.5V at J7 for the X4R Rx then I’m good to go with this Airbot F4 V3
As regards a board replacement the OmniF4ProCorner and the Matek F405CTR appeal
Hears hoping for a steady hand when Postman Pat arrives Tues with the goodies…joe