Am I good enough for the £33's?

I'm hoping someone here can give me some insite into the likely ROI when 4 tabling at the $33 level given my record of 4 tabling at the $22's. I'm trying to move up but whenever I do I'm just not getting the results I'd hoped for.

I play on both Party and Empire and my record is:

Party:
$22 391SNG's +$1918 +22.30%ROI 42.20%ITM
$33 38SNG's -$144 -11.48%ROI 26.32%ITM

Empire:
$22 350SNG's +$1560 +20.26%ROI 41.71%ITM
$33 121SNG's -$333 -8.34%ROI 33.88%ITM

I know my sample size a the 33's is small but my initial results has made me wonder if I am actually good enough to move up. Given a 20%ROI at the 20's what ROI would you expect to get at the 30's?

Any advice or comments are welcome!

Imajika