Tracey:
You cited SFB's "Floating maps", along with the traditional vastness of space, as the rationales for your map sizes.
However, the original map sizes were determined to balance 2 factors, the above vs. the fact that, theoretically, a captain can "disengage" at will by accelerating to high speeds, or by increasing the separation to such a point that they can't track each other anymore.
While your maps enhance the need to run for the "disengagement by losing tracking" method, there is no means to "readily" disengage by acceleration (short of a long stay at combat speeds).
IIRC, one of SFB's floating map balances was the fact that, after spending 1 turn at your maximum attainable speed, you can elect to disengage instantly.