The standard filter touches the pipes on the rack and wont go into place, but the suzuki alto one seems fine so far, but only had the car running for about 25 minutes checking for leaks and topping up oil levels, etc.
That's good news that you have adjustable rear ARB's....... cold wet weather soft, hot grippy dry track hard... obvious I know.
First time out, I set them stiff thinking the OE ARB's were stiff. Spun the car twice on my first trial at KH.
I set them slack and the car did not step out the rear..... You have more permutations now... play with NS / OS tyre presures as well to try to find a sweetspot for your driving style.
Remember KH in my pulsar. Sleet coming down during drivers briefing, running Pirelli RS5 tyres. Rubber was like leather, think I nearly spun on every corner on the track. Embarrassing. Lesson learnt. Hard rubber, zero degrees doesn't work