But you won't be travelling at 100kts with a 500ft/min desent with no engine. Your forward speed will be much slower.
Also, you need a pretty good day to make FL100 if VFR only.
Agreed, should have calculated that for around 80 knots. Point I was making though is there is a little bit in the middle where if it all goes wrong you will get wet, but it's not the whole leg.