Forget all about a G5RV. No sooner you modify it, it will no longer be a
G5RV. It was designed to be useful with an easy impedance match only at
14.15 MHz On other bands it cannot be no better, and is usually worse, than
any other random length supposedly multiband dipole.

All you have to do, to obtain the best possible mutliband dipole for your
back yard, is to erect a high dipole of any length which conveniently fits
into your backyard, fed via a 450-ohm or 600-ohm transmission line, of no
particular lemgth. The most important component in the system is the Tuner.
Invest in the tuner. It will last you for years on all bands. Ideally, have
one tuner for 10 to 30 Mhz and another for 1.8 to 7.5 MHz. You wont regret
it for multiband operation.
----
Reg, G4FGQ