Can't offer any advice on the positioning of the battery but I can understand the logic of better weight distribution.
Another useful tip re the battery on the GTi is to use a ratchet strap to secure it to its mounting tray in the engine bay. I had real problems securing mine as the mounting tray fixment strip just didn't do the job at all, it's now solid as a rock in there....the ratchet straps cost about £7 for 2 on FleaBay.