has anyone done this? I fancy having a go at it - any advice or tips?

I'm tempted too

Yes I did.
First thing I noticed was lighter steering! A little surprising. Then of course better turn-in and less understeer too.

I did make a guide here for it 2004, but I think it's gone now..?
However there are some pics on this page:

http://sfk.ibk.se/forum/showthread.php?threadid=5311
(it's in swedish but you can follow the pics a bit..)

Some niggles I've fixed:
You have to use a gelbattery, otherwise the usual vented acid can drop on the ground (via the vent.hose thru the floor) and cause bad damage to the cars paint, via the turbulance behind.

Also, use a sligtly larger cable than I did. I used around 10mm cable which gives too much resistance over the extra length.

Finally; you're better to use the existing hole behind the left front wing instead of drilling a new one like I did.

Good luck, it's well worth it in my eyes!

The reason I haven't done this is that the car is already unbalanced to the drivers side and taking weight from the passenger side will make it even more unbalanced It isn't like LHD in Europe where the drivers weight is counteracting the imbalance - in the UK we sit on the side which is already heavier

If you want to do something then IMHO move the battery further back, move it lower down or even fit a lighter battery, but I strongly believe the net effect on handling of putting it in the boot will be negative.

Yep.

You will need about 5 metres of battery cable. You will need to run it from the front to the back (under car or through the magic grommet) and you will need a little bit to create an earth in the boot.

Si, if you go to http://www.cpcbatteries.co.uk/ speak to Henley and say i sent you, he should / may give you discount (old friend of my dad's)

You can always put it on the rear-left side/ inside rear wing on UK cars then. I know someone had a tilted gelbattery in this position.. (Begbie?)

but then you are heavy on the offside of the front 'axle' and nearside of the rear

This is mainly a 20V/20VT problem I believe as the engine is less central than the 16VT

Try it John you'll like it!

Per, how long have you had the gel battery in place? Which one did you buy, and have you had any problems starting in winter? Cheers!

I've just started having 2 x 18Ah batteries, one was not enough.. I hope this will do for most situations.
Then again, a thicker plus-cable than mine maybe would have solved this problem.

I bought mine from Biltema: http://www.biltema.se/products/product.asp?iItemId=105080
699kr, around 75euro.

If my car was LHD I would, but as it isn't I won't

Per, do you think the need for the the extra battery is due to the length of the cabling? So if you'd either kept the battery in the front or as you suggested fitted thicker cabling it would be ok to run with just one gel battery? Cheers

I suppose so yes.. At least if you're not standing around pumpin with your stereo!

And the std battery worked well at the rear, it was just that eventual problem with my destroyed paint..

Turn the engine round?

The weight of the cabling alone should put you off this idea!

Get a 7kg dekka battery or suchlike + mount it as low as possible in a similar position to the factory one

5kg odussey battery 145e. small, and can be placed at any position.
and make a new place to it !
weight saving : 14kg at least, if you make that new place from aluminium and carbon, or fiberglass.