Best thing I've found to make it easier to get a GL1500 up onto the centerstand, is to make sure that the axle for it is Greased! The ones I've seen are typically dry, rusted, and have grinding marks from metal-on-metal wear.
Steps: (Takes 1hr)
1) Set bike on side stand.
2) Remove left muffler (after removing saddle bag, etc)
3) Add COINS (pennies) to the slots in the spring, to the center stand... use pliers to insert as far as possible.
4) Remove spring to center stand, while in the Up position... The spring will barely compress, due to the coins.
5) Remove cotter pin on right end of axle to center stand.
6) Remove pinch bolt to axle, on rt side.
7) Remove axle to center stand, by pulling to left.
8) Remove center stand.
9) Drill and tap a hole in the middle of the centerstand... Insert a "Zert" Grease Fitting... Both mine required a washer between the fitting and the stand, to prevent the fitting from entering the hole too far and interfering with the axle.
10) Use a grinding wheel to make a "shallow spiral shaped groove" across the full length of the axle... This will be the Path for the grease to follow, when you inject it via the zert fitting.
11) Grease the axle, the reverse steps #1-8 to install.