Wanted to add something to this thread I found after doing my own 535 conversion. The battery problem on the 990 might be even worse than the 950 given that the EFI shuts down and needs to reboot when cranking it over with a weak battery, not to mention running the pump.
I fitted a 545 in to 1050 Tiger with no problem when the battery failed in the cold after only 6 months. After 2 years my 990S Adventure went the same way so rather than fit the same battery I swapped in the PC545 but as UK_Mouse says its not as easy!
UK_Mouse can you update on your battery? How has it been over the last few years? I spoke to someone with a blue 950 who had swapped in the Odyssey battery and used the metal case as a battery box, he said the vibrations knocked the end off the battery eventually! Could it have been the same bike?
Anyway here are some pic of my own conversion keeping the vibrations problem in mind! It mounts on to the existing rubber mounts using the two captive bolts with some top hat spacers which allow the whole box to sit higher up between the cast aluminium brackets. This means the bottom of the box doesn't get close to the bash guard so the rubber mounts still get to do their thing. The box is also lined with about 8mm of sticky foam (two layers of adhesive wood flooring underlay) as is the back of the lid which clamps the battery in place. Fuel pipe is routed the same as UK_Mouses after I found the nice plastic clips in some of the pics hit the bash guard! The original accessory mounting plates were straightened out a little and bolted on the sides of the box, rubber pads put under the contacting areas and then zip ties run under the box to stop any vibrations. Everything is then installed and clipped on to these plates as it originally was. Funnily the bit I'm most pleased with is the rubber stopper off a table leg I cut down and drilled a hole in the side of to feed the positive wire through and protect the positive terminal from shorts
Hope this is of use to someone, thought it was about time I put something back in to the forum! I'm working on casting a new seat foam for the bike, will post when some pics soon.