Awesome info, thanks! I shot a TS2 Green at a local CZ vendor day & really liked the thumb rest. I'm not really in a hurry to make modifications, but in my research had heard there were issues with the CZUB magwell not blending to the frame as well as it should. My TSO is being shipped from a Gunbroker auction he won (he got it for only $1275), so I won't have it in hand for probably a week or so to see if that's an issue or not. I get to go to CZ Custom tomorrow (visiting the in-laws in Phoenix) and may grab the extended safety to save on shipping, then wait on magwell & mag extensions for the time being.
Edit - and I decided to switch to a race holster (Ghost Hydra), so not as worried about the thumb rest/holster situation. Was also looking at the Fire 4 Effect enhanced thumb rest.