Ross those frames arent light at all. I would ditch them. Like you say theres still a lot of weight in the car. bet the rear spoiler didnt help much either scooping all that air.
The front bumper does have quite a lot of filler! Jay will tell you that...
With a bit more height and stiffness on the rear and weight removed I recon a 13.6 would be poss
Did you run the sc car with r888s? I guess you ran it yesterday with the road tyres...?
Glad it turned a few heads