Great pictures and detail Mars, looks like you're going to have a superb example when it's finished.
Losing weight to better fit your Sammio? Now that's what I call dedication!
Before I saw that you've had Intertrim seats modified to suit I was going to suggest you take a leaf out of Lamborghini's book - on their flagship Sesto Elemento they've dispensed with the seat base to save weight and just fixed pads to the floor -
If you find that your head is sticking too far up into the slipstream with your conventional seats it's something you could consider.
I'd fit a slim, angled pad on a solid backboard for the backrest and 'velcro' another slim pad to the floor as the base. The further forward the base sits, the more laid back the driving position and the lower your head will be, but you'll also veer towards the long arms/bent legs 'Italian Ape' driving position that you had before you modified the front of your frame, and that used to be a feature of almost all sporty Italian cars.
That's pretty much how my driving position is and you soon get used to it so long as there's clearance for your knees. Mind you, I had a couple of Italian Sports cars a few years back so I knew what to expect.
Not sure if this picture shows what I mean -
Anyway, keep up the good work and I look forward to seeing more of your engineering solutions as you progress.