POTD Image Sizes? What Size Is Best?

So for the last hour or so i have been looking at various stats i have access to for Condom Cash and, the current Condom POTD site appears to be doing really well for a lot of affiliates however, the size of the image on the page is only 400x600 and i was wondering, do you think if i increase the size of this to 800x600 that it will have a positive effect on sales thruput?

I realize that the POTD tool is only being used to give surfers a sample quality of what they can find inside the individual paysites however, im wondering if i can increase sales from this tool for affiliates by enlarging the free POTD image a little, is that going to be worth the potential risk?

The old addage that comes to mind is..

If it isnt broken dont try to fix it.

So what are your thoughts on this, do you think increasing the actual viewable size of the image on CondomPOTD will increase signups for affiliates or, do you think it is worth leaving it alone and not risking a drop in affiliate sales from the POTD itself?

Regards,

Lee