I installed a Recaro Pole Position seat and this is what my planted seat base looked after I took close to 50% of its weight off.
It's really excessively heavy. And there's no reason for it as it only serves as an adapter between the chassis and the seat (which are already sturdy by themselves).

any pics of the pole position installed? does it slide easily?

I initially installed it with the buddy club seat rails.
It did slide well enough but they had significant play. Because I didn't know whether any other slides would have less play I decided to fix the seat directly onto a seat base. However, the planted seat base is heavier than the buddy club rails alone, which is why I flexed some material off (now the screws are also more accessible).

Since I'm the only driver I don't need it to slide and the passenger seat is still the original one. I primarily used it for autocross purposes and most competitors don't use slides either.

It's currently not installed (I'm not driving this car in the winter). I will post pictures once it is installed again.

Here you go.

I also made a buckle bracket such that I could get a belt buckle extension through that opening in the seat.

How easy was it to make that bracket for your driver seat buckle? Mine is currently sitting to tall to feed the OEM 3 point through the hole.

I also tried using the rear seat buckle, the length was perfect but its angled towards the seat so you can't buckle the seat belt in.

God forbid you get into an accident - how would you say these seats hold up? I've always wondered about that, especially if the seat or bracket are modified.

Sorry for the late response.
It's just a simple steel plate with 3 holes (2 holes are connected to the bracket of the baseplate and one to the belt buckle). The steel plate has about double the thickness of the belt buckle.
(One could also shorten the buckle and buy a second buckle for the original seat, but I chose not to because of safety concerns).

The new base plate is much thicker than the original seat base and there are no sliders. The seat is essentially directly connected to the chassis. So the seat would be holding up better than the original seat/sliders.
Also, the seat is FIA approved (stricter ruling than road traffic legalisation).

And all the parts which hold the original buckle are made out of much thicker steel than the belt buckle (so the belt buckle would be the first part to fail).

The only thing which is missing is the airbag in the seat. However, my daily-driver doesn't have any airbags in any seat either and I don't plan to install any.
Besides that I've driven motorcycles and flown small planes and grown up near a farm with tons of hazardous machinery which all is statistically more dangerous than driving a car: I always buckle up, don't drive drunk and don't drive above speed limits on public roads, which provides more safety than any number of airbags can.

Did you have any issues bolting the planted seat base down? It doesn't look like there is a lot of clearance for the front two bolts so I'm worried my wrench won't fit in the space. Also, what was the best way for you to find out where to drill the holes in the seat base?

How much for your front seat(s)?? :lol: But seriously

I bolt the planted base down first, then the recaro side brackets. Then drop the bucket between the side brackets and bolt them in. I sat the seats on the planted brackets and positioned them to where I wanted and marked then made my holes

Was there any trouble with the front two bolts on the seat base? The clearance to be able to torque those front two bolts down looks slim at best.

We just use an 8 point wrench

The passenger seat is still installed and the driver seat is not for sale.
This is not my DD. I use this car primarily for slalom racing. Not sure why this is supposed to be funny. Don't they have hobbies in Canada?

It was is an inside joke. Mah bad.