I actually like the standard seat unit fitted to the TRX, it's neat, as minimal as it can be yet will still accommodate a pillion if required & has decent storage space too. That said, the rear light looks like an after thought robbed from another model to me !
I wanted mine to look more at home without looking like I'd messed with it so here's what I did.
Bodywork off, light off, I cut out the piece of plastic that the light unit mounts to trying to follow the lines of the rear lense as much as possible to leave this shaped hole. I used a combination of stanley knife & hacksaw blade to do this bit.

Still not enough room for the light to go back enough & sit comfortably (look right) so I errrrmm... . modified my rear subframe tubes slightly using my favourite bashing stick.

I also used an angle grinder to shave a few mm from the light unit itself where it touched the tubes as there is only so much room you can gain from bashing them.

Once happy there was enough room for the light to sit where I wanted it I re-positioned the modified piece of plastic that was cut off then drilled & riveted it on using washers behind the rivets so they don't pull through the plastic.

All that was left then was to prime & paint my frame & bolt everything back on.



The end result still looks like a TRX light unit, just not so "in yer face" so to speak.

Could have got it to go in further by riveting the plastic mounting piece on the other side but I didn't want it to look like I had messed with it.

Some might think it's not worth the effort but I'm well happy with the result and I don't cringe every time I look at my rear end now.
Sorry some of my pictures are a bit fuzzy, I'm not allowed to use the GOOD camera for messing.
