Goldseeker - I forgot that you have curved guards - you need the valanced type to use the brackets as they need a vertical surface to bolt to. Is it possible for you to make another curved support on top of the mudguard but make the mounting ears a bit lower? It would probably be best to offer up the seat first without the bracket and locate it at the front and adjust the rubber buffers on the single seat mounts so the seat looks right. Then you will be able to get an idea how low you need to go with the curved bracket at the rear. (Perhaps make a pattern first with a bit of soft ally bolted to the guard and then bent in situ to suit the seat height). Sounds like you may well have a market if you make a few extra.
If you talk to Mike at Lyfords he may be able to describe the RGS bracket - he is very helpful.
My brackets came today from Lyfords and I tried them on the spare set of holes in the guard and the seat sat lower - just enough to get fingers under the back against the guard with a polishing cloth. I may take it a little lower by elongating the holes on the L brackets but I would then glue a piece of HD foam on the seat base out of sight at the rear in case the seat flexes a little with a pillion passenger and marks the paint on the guard. I ordered rubber buffers too and they fit a treat over the top of the redundant bolts used for the single seat option and support the middle of the seat - perhaps I will add a spot of contact adhesive to stop them falling off but once the seat is in place they cannot move.
I will add some pictures when I have finished the job.
BTW, those of you with Wassel seats will not need the rubber buffers as I noticed on my Wassel that there are some built-in rubber blocks which rest on the frame tubes each side.
Jim