Indeed, fitting the larger sprocket at the back has shortened your wheelbase if you are still using the same length chain.
Best off getting a couple of additional links put in...or if you are going to keep it like this for a while, perhaps a new one chain altogether. (tsubaki HD gold X-ring = £65-70 approx).
You really should be aiming to get the hub as far back as possible in the hub rotation...it makes a huge difference to the stability of the bike.
Once you've done that, and the chain is the correct tension, adjust the ride height back to suit. Sounds to me like you need a ride height tool
Shazzams table above holds the key...looks like 96 links are needed if its a 14 or 15 tooth front combined with your 39 rear. This looks as though is will give a good long wheel base at either +4 or + 8mm.
[Edited on 5-3-2005 by Harv748]