Answer - VERY!!!
I spent an hour yesterday and 3 hours this morning making the base for the seats only to find my measurements were wrong and the holes were in the wrong place. So, start again, triple checking the measurements. go to fit the seats and find that the bolts holding the bottom sliders to the chassis foul the bolts holding the upper sliders to the seat.
Has anyone had this before?

my seats come in two pieces, the back and the actual seat part. the backs are velcrowed to the bulk head and the seats are sat on!(not even fixed just loose)body weight holds them in places

EASY

We spent quite a long time, too. Measured the location for the holes, drilled them and found out that the threads were slightly angled in the seat base, so the bolt didn't fit in them, had to re-align the holes in the floor with a file...
But it's all part of the build, nothing serious here... such a joy when you sit in the seats for the first time...

We've all been there... or lots of us!

Yes, my back still hurts from putting ONE seat in... last spring; and I have to do it again to put carpet in. Can't wait for the passenger seat. I'll call the physiotherapist right away. It'll save me time.

Handy tip I learnt fitting my cobra seats. I needed some 16mm box section to lift the seat high enough to allow the runners to move.

Trying to drop the seat with the bolts in situ through both the box section and floor was a right pain.

The solution was to put a nut inside the box section and wind each seat bolt through it's relevant nut inside the box. This held it loosely in lace with enough movement to line up with the floor.

Saved me hours or screaming and cursing and allowed the seat to be fitted in about 20 minutes.

The first seat where we hadn't thought of this idea though was a right pain and took the best part of an hour.

Nigel

did it in about 3 stages.

fitted the runners to the drivers seat making sure they were parallel

did the passenger seat doing the same each took an hour ish before I wash brave eonough to drill the holes in the fibreglass.

Then fitted the drivers seat to the car. 1st drilling of holes was slightly out so opened them out a bit and fitted some big washers.

Then sat in the car going Vroom Vroom lol

Must admit it's easier to make them than fit them especially into confined spaces like a 7...doddle to fit in a Mini though

Yes, but a Mini is like a Lincoln Continental compared to a narrow bodied 7!

A wee bit of patience and a fag when things get stressy helps wonders....

You know, I was actually suprised by how difficult it was to decide on a good solution to mount my seats. Also to make sure they were dead straight and centered to the pedals was a lot of measuring.
Ive driven some cars (ac cobra replicas) where you sit on an angle and hated it. Didnt want that for mine.