Well, It sounds like you have it pretty much figured out...I used to wire nav equipment into sailboats so I can appreciate what your dealing with...

I have my wires running through the risers ,-)

Thunderbike risers

I had a similar project with an overhead dash on a sand rail. The relays I originally used were weak and did not stand up to the abuse of off road driving. I replaced them with relays from a local 4X4 shop and they have been working well. they were sealed relays and included rubber mounting pads.
I am sorry I don't know the brand name but they came from Karl's Custom in Mesa AZ.

Rondo, I'll be using stock contact relays for the project but if they have trouble with the vibration, I'll move to solid state critters (no moving parts); cost is an issue with this option though.
Is there any input on the potential down-side to drilling out the risers? I don't want to solve one problem just to create another - that would incur the wrath of the gods of good engineering.

Reperio

No problem with the size hole you want. I've seen risers with larger holes in them than what you want to drill.

Make sure you have a connector on the end of the wires that will fit through the riser bolt.

Doc

Thanks for the reassurance Doc. Relays are wired to a terminal strip and the individual wires screw-terminate to same.

Reperio

As I said .... once you have tried it out (read guinea pig ) I would be most interested to know how it's working out.

Doc

Have half completed the project of running the wiring through the bars and down through the stock risers (99 R). So far so good. I have installed a changeover relay in the headlight shell to look after the hi/lo switching and a single pole relay for the horn. Thought a bit harder about it prior to picking up the first spanner and came to two conclusions
Firstly, the more of the stock wiring I could retain and still comfortably run the wiring through the bars, the better.
Secondly,'anti-litigation' features masquerading as safety options could be dispensed-with altogether.
Withthis in mind, the clutch switch has gone to the god of unecessary wiring closely followed by the flasher switch and wiring. If, after 38 years in the saddle, I can't remember to select neutral when I start the bike (or at least pull in the clutch) then I need a kick in the arse and shouldn't ride a motorcycle. As for the flasher thingy; I owned the R for two years and have never used it - out it goes. There is a way to re-install it by simply daisy-chaining it to the hi/lo switch, but for now I won't bother.

The result is VERY tidy and I am happy with it. The only outside help required was drilling the risers. Ended up having them line-bored 5mm on a lathe for accuracy. I then drilled out the LH riser to 6mm to accomodate the additional wiring on that side (even without the discarded wiring) I'll take some pics if anyone is interested.

Reperio

Pics please.

Doc

I'll get on it Doctor.

Reperio