I recommend you start by measuring the individual wheels in relation to the body lines. Quite a few cars seem to show some asymmetry. By taking care to get this right, custom spacers can be used to rectify the discrepancies, should they exist....
Huncentric can only be used if the spacer thickness allows the use of low profile bolts. These are deployed and countersunk to the mating face of the spacer to attach it permanently to the hub....It requires a minimum of material ( thickness of spacer) - usually at least 20mm. I mention this because, as others have stated, 25mm in the rear is a shed load imo. And way too much up front.
I have 18” rims on a 4200, it’s lowered to 5mm below the oem GS ride height, and I have arrived at reducing the spacers, as the front especially, popped out of the arch. This isn’t kegal in the UK I understand. No tread outside the body lines ? Plus it looked a bit weird. And it rubbed at full lock ( also an MOT fail I believe).
Running 16mm rear, 12mm fronts. It looks perfectly normal. The wheels aren’t tucked under whilst they don’t protrude either.
I have no clue how FD get their super fat kits to fit without looking a bit ar5e at the same time as getting some rubbing somewhere....That said, as you are running standard 4200 ride height, you will likely have scope to add more than a standard GS without rubbing or spoiling the appearance.
Watch bolt length in the rear if you use slip-on types parts too - too long and they foul the handbrake mech....
Look forward to some pics of it done.
