I was thinking of moving the receiver up next to the rudder servo, although I have a similar setup to the current one in one of my other boats, which doesn't seem to give any problems. I'll give it a try as it is and move it if necessary, it's only held on with Velcro.
I have a 12v / 7Ah Graupner battery, which gives a few pounds of ballast, so I should only need to add a few small pieces of lead additional to that already installed for final trimming. The existing lead pretty much holds itself in place, as I have moulded it to the shape of the hull however, once final trimming is complete (and any excess lead snipped off) I shall fix it permanently to the hull.
The battery should be OK with the ESC.
I'm holding the battery in place with the pieces of wood and, for the base, strips cut from a non-slip mouse mat to stop it sliding forwards.
I have used "No More Nails" to mount the motor, as much as an experiment as anything, as it has done a sterling job of holding up a set of blinds at home, which take a hammering.
My alter ego - Captain Clumsy - managed to spill the best part of a large mug of sweet black coffee all over my instruction booklet and work area this morning so, after a two-hour, frustration-removing attack on a huge pile of ironing, I am now working in a sepia hue, which I have to say is rather calming, if a little sticky.