I always use Schumacher Tubby inserts. You'll get slightly more grip low speed from softer inserts, but the tyre will collapse on the carpet sweeper. I'd just stick to Medium tubbys.
A bucket of industrial strength acetone (not nailvarnish remover) is what you're after for tyre removal.
Cut the tyre, remove insert (you dont want the insert in the acetone as it ruins the insert, then plonk the wheel & tyre in a sealed bucket with 3 cm of acetone in the bottom. The vapours wil loosen the glue.
you can get the acetone here:
http://www.ecfibreglasssupplies.co.u...0-acetone.aspx
I can pick some up for you if you want, (they sell the sealed buckets aswell) as its near my house.
I used minipins on Sunday, but I think mini spikes would be easier to drive. My car was very 'tippy', often on 2 wheels, and quite difficult to drive. You can see on the video from the A final how often my car is on 2 wheels
I tried new mini spikes, for one lap, but they wouldn't have been any good until they'd been used for 5 minutes to wear them in, and I didn't have that run in time, so I went back to minipins.