How did you determine the dimensions for your frame so that it fits the height of the steering wheel and the distance of the pedals?
I did the base first, by looking overall dimensions on existing rigs, width of my seat, width of the pedal set I was intending to order.
Then I ordered wheelbase and pedals kit before going further. Below you can see first time I placed pedals on the rig to get an idea :
After that I cut some temporary posts, sturdy enough to hold the base in place and I seat in the rig to check how the position felt :
Vertical posts are set in place by clamps :
I started with posts a bit too high and from there I was able to shorten their length until the fit was good. And as they were just clamped it was easy to move them forward or backward to find the right spot.
To decide the placement I used the info that many rig makers give : you should be able to rest your wrist on the top of the steering wheel with your arm extended + a natural height of the wheel.
For the angle of the wheelbase, I measured the angle of the clamp that comes with the kit to fix it to a desktop and I replicated it on my mockup. I hesitated to do a flat beam and simply use the clamp to fix the wheelbase, but that was a bit cumbersome with the screw for the clamp being between the knees.
After the initial testing I understood that laying the pedals flat on the base of the rig was not good and that I needed to angle their support plate.
And finally, the seat comes with his rails that allow horizontal adjustment, so it is easy to enter the rig by pulling the seat backwards, and adjust your placement once seated. It also has a setting for the angle of the back, but I ten to use it as is. I flipped the headrest so it can't interfere with the back of PSVR2 headset.