So I purchased the Gary Fong collapsible lightsphere for my SB-900 flash. The flash was to wide for a comfortable fit. I noticed there were two types of flanges inside the lightsphere one was short and hard and the other was twice as long and soft. I thought of the idea if I cut off the longer flanges to the point were they were even with the shorter one would that offer a better fit and be a lot easier to get on and off. I emailed Gary Fong and asked him if they had done it before and would this ruin the integrity. They emailed me back saying yes it did work and did not ruin the integrity although the warranty would then become invalid. I thought for an inexpensive item why not. I proceeded to cut the flanges off with a scissors and after a couple of minutes I had flexible plastic confetti. I tried the fit and it was much better. Easier to get on and off but yet still maintained the hold and did not seem to put undue pressure on the flash unit. It is loose enough where I can wrestle the filter holder on the flash.
Disclaimer: I take no responsibility for this advise and please proceed at your own risk. I own all of the products mentioned and I am not endorsed by anybody.