OK right now I don't have time for the final tests (am still without a device) but I suppose it works. let me know if it does.
Update: it does work 
but I will post another package today that will not allow this to run on CDMA treo pro just in case idiots manage to run this who don't read which device this is for (forgot to do that check in sspl exe properly).
Instructions:
first, if you have GSM treo pro (NOT CDMA, NOT SPRINT/VERIZON/TELUS), this is for your device.
steps:
0) if you have Vista or Windows 7, make sure you have latest WMDC.
1) download Hard-SPL package from attachment, extract to an empty local folder.
2) you must Have Phone Synced with PC in Windows Mobile!
3) run PANTHER_GSM_HSPL exe from the folder
4) follow steps in the program!
5) it should go to tricolour screen now, i.e. SSPL mode, and show
0.59.C-SSPL. now follow steps in the RUU that's launched by now.
6) SPL flashes, device automatically reboots, job done. if you get any errors, follow the instructions offered by the program.
7) to confirm you got it installed, go into bootloader mode (tricolour screen!) and verify the screen shows 0.59.CMONEX.
NOTE: you will not see the SPL version during normal boot!
to enter bootloader mode to see version: with the device turned on, press and hold the Camera button along with the Power button, then press the reset button with the stylus tip, then release the Camera and Power buttons when bootloader tricolour screen appears.
NOTE 2: anyone having problems with the device entering SSPL automatically or problems with USB connection after SSPL was loaded, please copy SSPL-Manual-PantherGSM.exe from the
SSPL-Manual-PantherGSM_V059.zip attachment to the device and run it (device must be plugged in to USB). then once the screen is in SSPL, run CustomRUU from
Panther_CustomRUU.zip attachment manually and flash NBH file from
PantGSM_HardSPL059.zip.
NOTE 3: this is unsigned Hard-SPL. no limitations on flashing ROMs. also, this has overwrite protection, if someone needs to revert to stock SPL for warranty reasons, a stock SPL downgrade package will soon be posted.
NOTE 4: do not use this RUU to flash anything else! this is only intended for flashing the HardSPL.
finally, if you wish to thank me with a donation, you can do so by clicking the link the HardSPL program offers, or here: http://hpcmonex.net/htc/pantc/panther.htm