Downsampling VST instruments

I have been sampling VST synths into Halion 6. I was finding that sampling at 16bit I was losing a really noticeable amount of high end and the reproduced sounds were very dull sounding compared to the originals. If I sampled at 32bit float the sound was much more accurate. But 32bit multi sampled instruments will be gigantic! Anyone have any tips on sampling down to 16bit without losing quality?