-high pressure slicks
-smaller saddle (think MTB width, mounted higher and further forward than the standard fat springy beach saddle)
-BMX cruiser bars slanted forwards a bit
-and then work on the gearing
What kind of BB does your cruiser have? if its got dodgy one piece cranks, you may want to upgrade it to something stiffer, with bearings less likely to develop play. Thats usually the first thing to go on hard ridden cruisers.