This shuttle is something I threw together. It can lift 31.5 tons to a 100km orbit while holding 8 Kerbals. Must launch with SAS and RCS on
action groups
1= orbital maneuvering engines.
2= shutdown the Main engines
6= Opens cargo bay.
Throttle up on launch then second stage fires the solid boosters. Nose it back just a bit and throttle down to 3/4 to keep prograde strait up until about 5000km and throttle back up. Solids are out about 5500m and stage. Try to keep the nose back so the prograde marker stays up and start gravity turn around 7000km. It takes it a bit to ease back so it's not a big deal to start that early.
The top three small tanks on the main tank are turned off. When the bottom tank is half full you will have to transfer fuel to keep balanced. I start from the bottom and work up, leaving the top tank for last to keep my nose heavy enough to point to 90. I leave the shuttle tank turned on but stage and drop the main tank before using it.
After throttle off and stage main tank, I switch to orbital engines and turn off the main engines. The bottom orbital engine should be at 50% thrust limiter but in case it isn't you may want to check because it will cause it to nose up.
You should have plenty of fuel to do all kinds of maneuvers and return.