Indeed Bob (well you couldn't wind it down to 930 I think) I agree. What would you actually do then in that circumstance, maybe wind it down to the nearest thousand and subtract it? I think I would just add on another 35 hp's and call 1,000' sea level.
As an aside the highest airfield I visit in UK is around 825' ASL (Crosland Moor at Huddersfield) so you would have to wind down another 30 hps to get QFE for that field. IE have an altimeter that spun down to around 900 hps or less.