Thanks for the reply Kitwin,
I have Bandsaw, Pillar Drill, Heavy Duty hand held Router, small selection of taps/dies and the usual home mechanic/wood worker range of tools (heavy & light duty) and not afraid to try something I haven't done before (hence here ).
I had read that larger than 15mm rails are better, but is it better to use larger bearings as well ?
I'm trying at this stage to get to grips with what is better for strength/rigidity and direct my design/expenditure towards the most influential areas.
Roger