I wouldn't suggest deleting the stock ROM..... Since its Verizon you have a locked bootloader and can't flash kernels via safeatrap (safestrap can't flash kernels anyway.) So if you delete stock slot you pretty much delete kernel if I'm right, and you can't Odin it back to stock I don't think because of the bootloader..... So yes make a big backup of the stock. If you want to take the risk of erasing and having a brick you can try it...... Safe strap can only flash touch wiz ROMs because it can't touch the kernel since the bootloader is locked.....

Sent from my Rezound using xda-developers app. CyanogenMod 11. S-off
Main Phone:
Verizon HTC One M8
Insert Coin And Paranoid Android
Main Wifi Device:
Sensified Locked S3