That is what I said earlier: "You would also have to play with this new icon's alpha level in the Navigatemap.ui file (under common\ui), quite simple, you will see!"
You have a name for your icon, just replace btnNMB_MSN_onmap by your TMC icon name (btnNMB_TMC_onmap ???) in NavigateMap.ui under common\ui, in 3 different places in that file I think, just search for the btnNMB_MSN_onmap thing.
Let me know.
P.S.: I wll make it for you, but I need the UK version of V2.75!
Chuck, you can't just change the button or it's characteristics and have it go to TMC. It is an entire line of script that has to be changed. If you are interested in putting in a UK version for your 2.80, PM me and I will send you the files and the scripts