Malcolm,

thanks for that reply - always good to hear from you! Unlike you I would rather turn the plane over and then only undo one screw! I have gone ahead with fitting the batteries into the pipe tunnel, I made a frame to support the front, with the rear of the batteries sitting on the floor of the pipe tunnel - see the picture. Two velcro straps hold them in place, with a velcro patch between the packs and under them, to stop them all from sliding relative to each other as you suggested.

Once I have my motor sorted (see my other post) I'll be good to go!

James