Skiddles, what RT forks do you have? I have the ones with the side screws, as in this pic:
Alex Ortner makes a set of radial fork bottoms which he used to fabricate for US based Cyclecat. They´re plug and play. I don´t understand why you would want 108mm over 100? Are you running race Brembos or cheap Tokico shyte? I´ll see if I can find a pic of Alex´s bottoms.