Wheel Books for Word Families

PLEASE HELP ME CHOOSE:
So I have been working on making word family wheel books for half the summer. (I know, it really hasn't taken me half the summer, but I've been working it out mentally for at least that long.)

I am trying to fill several needs with this project.  Most importantly, I want the kids to get excited and feel successful reading simple words.  I want them to be able to self check their reading skills too - peeking under the flap to see if they read it right.  After several different design styles, I've finally settled on this one (you should have seen some of the interesting styles I tried).  I like that there is a solid place to hold and easily make the wheel spin.  It has proven very straightforward to cut and assemble (one version I had had a hole in the middle that revealed the changing initial letter - but this just proved too challenging for little ones to poke out.)

Now I just have one last issue - the size of the pictures.  If I use the bigger size, the picture kind of peeks out and can catch (if it isn't completely glued down) on the opening as you spin the wheel.

If I make the pictures a little smaller, the pictures are completely hidden as the wheel spins.  But, they almost feel too small for little fingers to cut and paste etc.

Since it's still summer, I only have my little guy to try it out instead of a class full of "testers", I'd love some teacher feedback.

If you are willing, could you download this prototype and try the two different back wheels and LET ME KNOW WHICH SIZE YOU LIKE BETTER?  Other feedback is also welcome.  Please leave comments here - not in the store.

I'm assuming the assembly is pretty straightforward:  Cut the back wheel and picture squares first.  Glue the pictures under the appropriate word.  Cut the front wheel - and cut the dotted line (this makes the flap to peek and check)  Assemble with a brad (paper fastener).