Short answer to shortening the belts - you can't do it yourself. The tape and adhesive is super expensive and requires special equipment. It is kept on dry ice as it cures at room temperature. Carpet tape and filament tape are not the same. You don't want a 60 grit belt to unload into your face at 3600RPM. The choices are to make a longer arm for your grinder, or switch to a much larger wheel. If you could get some to a smith with a KMG or Bader, there would be no problem fitting them on for a grinding test.
Some questions to ask the store:
Are the belts Zirconia?
Were they made for metal grinding?
If the above two are true, several smiths on this forum (I would for sure) would be glad pay the $50 for the 100 belts,and make you a knife in thanks for middle-mannig a great deal. If this idea intrigues you, let me know.Even if they were wood belts, the deal would be good.
Stacy