With 6.2 Isc, you would get 12.4 aimed at high sun. Flat on roof is less due not being aimed. How much less depends on how high the sun is anyway, where you are at that time of year.
In May at 49N with a single 130w panel (8.2 Isc) and PWM I got 8.1 aimed and 5.1 flat at 10 am, and 8.3 aimed and 7.2 flat at high noon.
If you were there then, your 12.4 would be 7.2/8.3 x 12.4 = 10.75 at high noon.
Flat vs aimed less diff going South so at 23N on 21 June sun is overhead no diff.
Don't confuse ambient cool temps with panel heating temps. The panel gets hot in the sun even when it is not that hot out ambient. Just put your hand on the panel! I took some temps with my IR gun on the back of my tilted up panel aimed at the sun at different ambients, so I have seen how that works.
Yes, solar is interesting, plus it is even useful! :)
