Thanks for the additional tips Warzous. I didn't think of the low efficiency of the engines - swivel for launch and at high altitude terrier. By now I got down to 3650 dV VAC so I am satisfied :). Are any of those crafts anywhere on the forum?
Don't activate SAS, take-off, full thrust -> I take off with SAS until I do the turn at 50 m/s. Then it's off until the vessel is stable - with some fins up to 20km
Never go away from prograde circle -> this I have a problem with . The circe falls towards the horizon because I lower my thrust so I don't get too fast
Prograde should cross 45° at 10km (I like 8km with streamlined payload) -> ok, something else to work on :). But won't the rocket lose to much due to drag losses since it will be going fast? What is your speed at this point?
You should be on a shallow 10 to 25° trajectory (orbit mode) - I get there at less than 10°