what type of slider window should I buy?

I have a porch that currently has screen from the floor to the ceiling, 84" high. I plan to build a 24" knee wall then install 5' high sliding double pane windows. The knee wall will be 2x4 construction. The local Home Depot sells sliders with a nailing flange for new construction. They ask me if I wanted a standard slider or one that had a wider flange so that it would fill to the inside edge of the 2x4 wall. Which type should I buy? If I buy the standard ones I would have to finish the inside with some type of molding. This is not a problem as I have the required tools, but I'll looking for the easiest installation.

 

Guess it would depend partly on price. It doesn't take much to make an extention jamb , so if the "fuller" frame is much more, I'd make my own. Also, I'd make SURE the frame will come out flush with your finish wall if you go that route....including exterior sheathing thickness, stud thickness, interior wall thickness.....shame to get the thicker frame and STILL be a 1/4" short of being able to case right on the window frame !