WAV is a lossless raw format, so the short answer to your question is no.
The only way to reduce the filesize is to :
use a different export format, or
shorten the length of the project.
There are various lossless compression tools available to you such as WAVPack, FLAC.
The lossy compression tools that could be considered are aac or mp3.
Although FLAC encoding is always lossless, it still offers different compression levels to choose a tradeoff between size and decoding speed.
So, the unexpected difference in size that you noticed may come from different compression levels between the files.
Try to re-encode the cropped file with maximum compression level (8) and compare sizes again.
Hi there. I use Logic 9 and save PCM Wav at 22050hz and play back is fine. I'm not sure why you're getting problems with the speed?
20mb goes a long way if you use it efficiently. Keep files sizes low by saving as mono, keep SFX to <0.5sec. Loop SFX for longer instances. Use pitch changes to create variations.