+4 degrees of caster would be very heavy to steer.

I use to run +3 caster, -3 camber & 10mm toe out & that was heavy, more caster with less camber would be worse. I didn't like the looks of all the shims either, so I replaced them with pipe cut to the same length, slightly angled on one end.

Is it race only or road/race? How good are the tyres, what rims, what track does your rims give? If it's road/race, try +2 caster, then keep adding negative camber until the tyres wear evenly.

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Three 164's, Two 144's, One 142 & a partridge in a pear tree.