Setting up International Flat Rate USPS Priority Mail

I'm hoping Ajeh or another of the resident experts can confirm what I need to do.

I've been shipping domestically in the US for a year or two. Everything is flat rate Priority Mail. Flat Rate shipping module. Easy Cheesey.

Now, I need to set up international shipping on my Zen Cart store, and once it's working, it will be the basis for 2 other stores.

Here's what I'd like to accomplish:

1. Existing domestic flat rate shipping via USPS Priority Mail stays the same.
2. Add International flate rate shipping via USPS Priority Mail. Looking at the USPS rate documents, it looks like there is one cost to ship to Canada and Mexico, and another for "everywhere else". (I only need one box size, hence, there's only one price to consider for any location)
3. Obviously this is charged per order, not per item or per weight.

Am I correct in assuming that the easiest way to do this would be to clone the flat rate module 2 times, one for Canada & Mexico, and one for everywhere else?

Then I'd set up 2 zone definitions to match the above? Would I have to change my existing zone that I'm using for just the US? Originally I had deleted all the countries except for the USA. I've used the install sql to add the countries back into the database, and I can see and edit them.

I'm having a brain-cramp on the sequence I need to accomplish this. If someone could confirm my logic is correct, or point me in the right direction I'd really appreciate it.

Thanks!

I got this resolved. No further assistance needed.

For those that are curious, I cloned the flatrate module following fairestcape's incredibly perfect directions (here), then added zone definitions for the countries I needed. Tested, and it worked flawlessly.