One problem with the parameters in Concept 1 is that it is a very viable drive for bopping around withing a solar system - not between orbits, but say from Jupiter to the Trojan Points. If I want to keep the importance of jump drive down and preserve in system movement we have to push the jump limit out of the system entirely. This is not great for a conventional RPG. Travel times from 1 AU out to say 10 AU, which is just outside Saturn's orbit, run about 90 days within the fuel strictures of the design system we are using. But they are doable and I expect that I will get better at both ship design and mission planning. They also keep the Vmax below the scarier percentages at the speed of light. At 5cm/s^2 (5 milligees) we just barley break 0.1% light speed while traveling 9 AU's. With turnover we have a 4 month trip but could easily rendezvous with a refueling station in say a Saturn orbit.
So, flatness of space <6*10^-5 m/s^2. Solar gravitational potential energy at that point is about 90 megajoules/Kg . I will crunch some numbers for main sequence stars to see what sort of limits this imposes. And I have *still* not talked about jump distance.
A quick preliminary number crunch is interesting. Basically, if I am jumping to a less massive star, I have to go past the "flatness" criterion boundary in my own system to find a sufficiently flat destination in my my target system that has an equivalent gravitation potential energy. To jump to a more massive star I will jump to a target well outside its flatness boundary (Minkowski Boundary?). It might even make sense to jump up a ladder of increasing massiveness depending on the exact placement of stars and their relative masses.