Thanks for this explanation. I am building a "Tomboy Senior" 48" and the plans call for a 1.3 Mills. From what I read it might be a bit under-powered using an early Mills (I have just picked up a Mark 1 series 2 )and whilst a good series II would be better, I thought a 1.5 might be the answer.
There is an Irvine Mills 1.3 on eBay and that might be an answer (but its very expensive). I could just use a PAW 1.5 but was trying to keep it as "vintage" as I could.
Any advice?