I made dual wheels for my L185, which is pretty well the same tractor. In over 30 years it has not been a problem for the rear end! The overall width became 66". With single wheels I wouldn't go over about 60" however. The L245 came with adjustable wheel hubs. I would have thought their widest stance would be enough.
Mostly I agree with everyone else. Put weight in the back end! I had filled wheels on the 185, but still didn't feel stable without another 500-600 lbs on the back.
On my new L3200 I again have filled R4s - the dealer said it gave me 400lbs a tire. I have a 600 lb ballast. Together they do the trick.
Without the weight, you have a hard time digging out a full bucket...