well the timing belt has to pull the cams and when the spring pressure cam lift and ramp angle are dramaticaly changed this increases the stress on the timing belt. There was a thread on this in the type r forum on honda-tech a while ago and a bunch of people were wondering why they were breaking timing belts with newly installed cams in particular toda B and Cs with toda valve springs. Just something that I think is worth looking into. I also think if a stock t-belt is used it would be alot safer to use the type r/portflow spring combo after seeing a chart of spring pressures for the different types of springs out there.