Sizing Up A Composition

I've got a new piece brewing already. One of the members of my Michigan garden forum posted photos of tiny tree frogs sitting on her shasta daisies and generously agreed to share them with me for a painting. I'd like to make this at least a half sheet, maybe larger. I'm trying to determine how large I want each frog in relationship to the others within the composition I have in mind. This is a compilation of two separate images so I will need to do some adjusting.

I used edge detection in Irfanview and traced my line drawing onto tracing paper. BTW, I use my PC monitor as my lightbox. I then taped the tracing paper to a scrap piece of foamcore and am posting a photo so I can size things up(pun intended). Pretty rough at this point. PSP is outside my budget and I've about given up on my Elements 6. I think it's been corrupted. Whatever it's malfunction, it's just too darn frustrating to try and put together a comp with it. I'll have to use some ingenuity or just do it the old fashioned way and make umpteen drawings until I'm satisfied. I'll also need to take some photos of my own daisies to complete the scene.