I have alsways regarding the term "jump bubble" as an analogy and not as a bubble as such. I have always regarded the hull gridd being the actual gimo to keep the jump space seperate from n-space inside the craft.
And I have no problems with sub 100dt jump capable crafts. Why not? I think the limit at 100dt is an artifact from CT where everything was more or less designed by tables rather than formulas.
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Roger Malmstein
www.travellerfreepo