Ouch, I don't deserve compliments, I made a mistake XD.
Every time the number of objects is changed:
Set timescale to 0.99^NumberOfObjects
Every time an object is added:
Set timescale to TimeScale * 0.99
The first would perform little bit slower, but it would automatically rise the timescale back towards 1, when objects are destroyed. The second is faster but needs a separate event to rise the timescale back... :D
AND... 0.999 or 0.9995 seems better than 0.99, the scale drops too fast with 0.99... with 0.9999 the timescale is 0.5 with about 7000 objects.
AND... btw, lowering the time scale doesn't remove the fact that it still needs to produce the fps the v-syncing needs...