Well, you can fit 8 Singapore PP photos in one 4R in a 4 x 2 grid.
I just tried with a dummy photo, and the free option gives you 4 photos in a 2x2 grid occupying 1/2 the 4R area -- all this is in a downloadable JPEG image. The other 1/2 comes out green, with the website address and some text. All you have to do if you want to maximise your 4R print area is copy and paste. It's still faster than doing it all in PS, unless you already have a template set up I guess.