Yeah, I knew it was a bit of a necro...but this design is inspiring to me! The gear were indeed the issue. I moved them to the sides of the solids and now all is well. I'll need to keep this in mind when I build more SSTO rockets in the future. In the past I've concentrated on designs using the T30 and the aerospike, with the odd LV-N, T45 or mainsail tossed in when higher isp, control, or thrust was needed. I never thought that solids have their place in SSTO designs!