I got my wife a very neat Carrera Alu MTB frame. I need a 30,6 mm seatpost ... odd size it seems. Will a 30,4 mm post work???? Can I use (or turn) a shim and use a"standard" post 27,???mm dia. I have a suspension seatpost that came form my Trek 7200 or I can use the Kalloy post that is on her Nishiki. I am building the components over form her Nishiki. Any help would be appreciated as she keeps on pestering me to finish her bike!!!!