You can flash the ROMs with the RUU in the ROM package, should you have trouble with upgrading, try Mun's RUU (thanks for the tip Boto).
So no need to downgrade before upgrade anymore.
But don't flash ROMs containing IPL/SPL. -(This means do NOT flash an official Rom)
In order to flash an Official Rom again, you will need to remove HardSPL because flashing an Official Rom with an IPL/SPL with the patched SPL already installed, you will find yourself in the possession of a very expensive paperweight.
To remove HardSPL, you will just need to follow these simple instructions:
1. Download SoftSPL by the-equinoxe.
2. Download the IPL/SPL based on your device and carrier(attached below)
3. Extract SoftSPL to its own folder and then extract the nk.nbf file from the correct IPL/SPL to the SoftSPL folder.
4. Run Start-sSPL.exe and follow the simple directions. It is almost fully automated(your screen will turn white during the flashing process and it will appear to have crashed. This is normal so just proceed like normal)
5. HardSPL should now be removed if everything worked properly. Depending on your device and Carrier, download the appropriate Rom for your device:
- T-Mobile MDA Official WM5 Rom
- AT&T 8125 Official WM5 Rom
- Vodafone Qtek 9100 Official WM5 Rom
- Orange SPV M3000 Official WM5 Rom
- O2 XDA Mini S Official WM5 Rom
Please be aware, I take NO responsibility if someone were to use the files provided in this tutorial incorrectly and damage their phone.
USE AT YOUR OWN RISK!
Credits go to the-equinoxe for developing SoftSPL and making this possible.