Armchair Rocket Scientist

Thanks for the reply. I believe that the main issue is what you had stated in part 2 of your reply. I am unable to maintain positive pitch control over the shuttle, and as a result the speeds are indeed excessive for the altitude.

CSS does properly model the cut pattern in the SRBs (that provides variable thrust during launch), but I am unsure if real fules has broken that aspect. I have tried manually throttling the SSMEs, but to no avail.

CSS's aerodynamics do not function properly in RO, so I will wait until the CSS is fully compatible with RO before reinstalling RO (I uninstalled RO pending CSS compatibility because I would prefer having a functioning CSS over RO at the moment.)

Again thanks for the reply, and I believe it helped in determining the core issue.