i used kw parts to build a simple, five engine 2 stage to orbit rockets that can lift a 130 tonne payload to a 70 km orbit. Ill post a pic so you can see it. Here is a link to the photo: http://s1307.photobucket.com/user/RKirz/media/screenshot1_zps28e5cf21.png.html basically, out of the five engines on the main stage, two engines on opposing sides are droppable liquid boosters that feed fuel asparagus style to the fixed boster next to it, as well as the center tank. (this allows all five engines to run off only 2 fuel tanks, so once the strap on boosters are empty, you drop them, and continue on with the three remaining engines with full tanks of fuel *this happens at about 5-6000 meters up*) Asparagus staging is def. something to try, it will help alot. Also, don't be afraid to use struts with kw parts. All the tanks on the rocket i posted are cross braced and laterally braced to the center tank, while also being braced to the stage above. Also, try to set up triangular bracing across the interstages, as they are very wobbly (use the small cubic trusses as anchor points, as they will make sure the struts don't clip through the rocket) Also, if you want, pm me, and ill send you a download link for my .craft file if you want to check it out. Good luck!