Gen 1 top yoke modification

[gadget]

Hey all, as title suggests... I'm planning on doing a 'low/flat bar conversion to my sv650s 1999. I already have super low risers on order so I can use a nice flat bar and so hopefully won't have to cut the screen for clearance.
My question is this, ... as there's literally no meat on the underside of the top yoke to drill through to mount the risers, would it be preferable to infill with alloy welding and then mill of the excess or can the void be filled with glass mat and resin or maybe carbon fibre and resin?
I was thinking once the void on the underside were thoroughly cleaned and roughed up a little they would provide a good key for the resin to bind to!!?
Any thoughts / advice with either of these solutions?
Cheers peeps.