So I actually have a 181 and 281 XP on a 36" mill. I reworked both with new Meteor pot and pistons to bring them up to 88CC (a direct swap and well worth it for under £100). I use both of these saws running a 42" Sugihara solid bar on the 36" cheapo-alaskan clone as my "small" mill. I have an MS880 and 64" Panther Mill for the big stuff.
The 188/288's are fine for milling up to 30" or so, however they are significantly slower than the MS880. They have lots of torque, but not particularly high chain speeds, so you need to keep the rev's up and to be honest the best way is going to be a full-skip or hyper-skip chain. I've got hyperskip on the MS880 and it's awesome, makes milling so much easier and faster, the only down side is I don't think hyperskip is currently available for 3/8" pitch which is what these saws are running. I've got Oregon rip chain on mine currently which I believe is full complement chain and to be honest it's a bit much for the old girls - it's grabby and slow, so I could really do with finding a less aggressive chain, a 3/8" hyperskip would be awesome (@RobD).
To give an idea of speed, I recently milled a 28" diameter cherry tree approx 10ft long, this was taking around 4-5mins/cut through the widest parts of the tree, the saw bogged down a lot, so it was gently gently to get it through - I don't run a winch on my small mill and to be honest I think it would be "too much" for this set-up, light hand pressure to keep the forwards momentum is enough.
I'd say do the 88CC conversion, give her a re-tune and maybe a port and you'll have a decent milling saw for anything up to 30" regularly, maybe 36" occasionally (but it will be painfully slow).
All the best, Tom.