[FWTools] Need smooth sub sampling?

[Lance Dyas]

I almost have it... (I dont know if this is the right place I am 
modifying scripts
that came with fwtools)

By running BuildOverviews with "AVERAGE" like so

dataset.BuildOverviews(resampling="AVERAGE",overviewlist=overviewlist,callback=CallBack)

I can get a set of nice sub samples on my VRT(raster) this is all fine 
and dandy but only if I read
exaction the overviewlist... ie 1,2,4,8,16,32,64,128
 
 basically I would like non-integers
Or could I specify a sampling method in my dataset reading?