If you could get some video on your roadster that you could see what the rear of the body/chassis is doing, you can start the learning curve to getting this into the 1.30ft range pretty quickly.
Just by the info you supplied, you have the power, gear seems good enough for your weight too. IMO, I would start with the rear shock settings with changing from a 50% setting on the compression and go stiffer and watch your 60ft's, once you start dropping down keep adjusting until your best 60ft goes away, then go back to the last setting or your best 60' setting and then start on the rebound or extension of the shock, and that setting should be in the softest setting to start out with and work with that going stiffer again until you see moe drop in 60', seems like you may be too stiff on extension. One click at a time, and yes, it will take some time, fuel, and moe money for fuel but if it all works, it may pay for itself later when you go rounds
Your I/C does sound a little low and not very far out, but try the shock adjustments first, one change at a time with each direction EXT/COMP and log down your results so you have this info to go back too. I am gaining knowledge on chassis's but your roadster is a little lighter than my 3600lb Elky and I used to hit 1.40 60's on a 10.5 tire running 9.90-9.80 at over 136mph.
If you can't get better 60's with shock adjustments, you may need to adjust your lower bars, and try going up 1 hole on the front bracket only.
Wish we could see a few pics of the rear tires on the launch and what the back end of the chassis is doing, this may help out a bunch.
Go to the 4 link basic post on the top of this page and read this info., you should pick up some very good useful info from a few of these guy's thoughts. Good luck and keep us posted.
Elkyman
John