How did you attach the SRBs and external tank to the XR2. It looks awesome. Is it balanced because the space shuttles SSME thrusts provide stabilization during launch but the XR2s engines are much more powerfull. Nice work
I used velcro rockets to create this stack. It works very well. The current version, which I made a pretty crude looking launch tower to go along with it..there is an engine attached to the external tank as well, so you have three engines burning during powered flight, and the SRBs help take the stack up to about....2.1 km/s or so.
I currently have the autopilot set in Launch MFD to get the stack to a 260x80 km orbit, sub orbital very similar to a standard ISS shuttle launch. If you are interested I could PM you the files and you can give it a try.