Horus Lupercal
Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
Capable of getting to LEO, Moon and back to earth
Etherian Space Program, I seen this elsewhere and can certainly help out with this one.
This is based upon several assumptions, chief being an empty fairing at the top and usingna frontier for stage 2.
Easiest fix I can suggest is the powerpack. 25 thousand kN is a lot of thrust, you don't need 7 titans and 4 hawks. With a 656t launch mass, you can get away with 2 titans on the core and a hawk on each side as a booster.
That'll save you about 55t of dry mass as well, which will do wonders for your Dv score and probably even mean you can sack the boosters completely, saving you even more weight (200t)