Welcome to the forum. The Panama Jack should work fine if it has a steel frame. Aluminum frames have developed cracks on occasion.
I agree with GearNut on the coaster brake. Take your time with the build and it will save you hours of troubleshooting later. The experts can pull off a 4 hour build, but most of the rest of us can't without muchos problemos tarde.
“You're only young once, but you can be immature as long as you like" -Unknown