You would probably get an error since there wouldn't be enough space for AD's aroma to make a hardswap space bigger than the partition itself. If the error misses out then it would simply refuse to work.
P.S. Which one did you flash? I'm using AD also, but without hardswap and the AOSP version from the OP wasn't enough so I've made my own with 800MB /system.
Personnaly, I did not notice a great performance increase when using hardswap as AOSP ROMs already make good use of RAM and in any way far better than samsung do with their own devices !
BTW, is it that simple to change partition sizes: just change the update binary shell script by using starting and ending points of each partition ?
(Eg: for sammy zip, there are 1805-193=1612 MB for system which I suppose to be too much for ports)