Pedal ratio has a significant effect on brake feel & performance. Don't underestimate it.
But your pedal ratio is in the right ball park, so we've ruled it out as a major cause. Just something easy for you to check and soemthing that could be very wrong in kit cars.
I still reckon it's a brake balance issue. But that's only a guess as it's a bit hard to diagnose this here.
You definitely need a brake specialist. Brakes are something we all need to get right. Let us know how you go.
P.S. Plus I wanted to see if you could contort yourself enough to get in and measure the ratio. 
I was lucky and had the seats out at least.