Try using 1 R.A.P.I.E.R, it's all you need to get up and the extra weight really doesn't help, also, try a lower acsent path, about 15-20 degrees, if youbplane can fly vertically you have too many engines for an SSTO (you only need one rocket in space, and atmospheric engines are just dead weight. Wing design has little effect in the stock atmosphere, but with FAR it becomes very important, I find that delta + canard designs work best. Speaking of FAR, the best advice I can give is to use Ferram, it makes planes of all types more enjoyable to fly.