What Size Doggie Door?

[PookieMOM]

Ok, I'm in the market for a doggie door. I've looked at so many that I'm totally confused. Should I get a dual flap one or a ridged door cat flap? Does anyone have one that is great?!?
Here's the story.

I have 2 dogs, a 10 yr old maltese and a new yorkie pup named Pookie (4 months old) that can't seem to hold it through the night! I've tried crate training him, but crate training Pookie is for the birds! Regardless of how many times I let him outside he STILL pees and poos in the crate!!! And yes, it is as small as I can get! Yesterday I took him out 3 times during the night...never produced anything, then he went back to the crate and peed and pooed there!AHHHHHH! He is somewhat pee pad trained, when he's in his exercise pen he will pee and poo on the pee pad...but only if he is in the ex-pen. I can't leave him in there at night because he has figured out how to climb out of the darn thing. During the day he's ok, because he can see us and all the action.

So that leads us to the doggie door. We're hoping that a doggie door would be a great training tool since the maltese only will "go" outside, and Pookie loves to follow her and investigate. Sometimes he will pee right after her (yorkie see yorkie do effect) but he has yet to poo out there! And we've had him for about 2 months now! I've set up the ex-pen trying to trick the poor dog so maybe he'll associate "going" with the ex-pen. Lord I hope this works! Any advice would be appreciated!

[PookieMOM]

ok we got a cat flap, a Cat Windoor. It goes in the window(we have very low windows) so that I can just ex-pen off an area of the backyard as the poop area! And both the dogs are small enough to use it. I'll let you know how we like it.