Some very interesting points Perry. I thought about this for a while. Setting the speedloader nut behind the nut will compensate for the length. As for tension... hmm... On a 25.5" scale guitar the distance from the nut to the 1st fret is about 1.5" for a 1/2 step tone difference. So, the difference in tone from 25.5" to a 25" scale guitar (1/2") is about a 1/6 step micro-tone. How much tension difference would this be? Pretty small I think... and more importantly, within the range of it's "Range Tuning Screw."
... from the floyd rose webpage:
That quote above's mention of drop tuning and open tuning (using the same calibrated set of speedloader strings) makes me suspect that it is possible.
Well, anyway, the absolute best recourse for samdjr74 would be to join and ask this same question on the floydrose mailing list.