So here are the curtains installed in the trailer.
We have a blue/green colored bedspread so we picked up a medium blue curtain material. The material we chose was pretty opaque so we did not feel like we needed an additional liner.  We tested under various lighting conditions and you can't see through the material from the outside of the trailer with trailer lights on. You can only see faint shadows/movement but no real outlines of people or anything.   
We felt the original curtains were not quite long enough for our tastes because once closed, they are fully stretched from end to end and we wanted some level of pleat showing even when the curtains were closed. Therefore we went 1 1/2 times the window length which then required 4 yards of fabric to cover all the windows. 
Valerie first took some scrap material and made a small mock up so she knew what type of stitch she wanted to use. 
We made 4 front curtains and all curtains turn out to be the same size.  She cut each piece to 21" x 40". If doing again, she said she would have cut them to 45" instead to get more of a pleating effect when closed.
After cutting all the pieces, she ran the raw edges through the serger to clean up the edges. 
She then made a 1" seam on the left and right side, folded over once.  For the top and bottom she did a 1 1/2 inch seam.  This allowed it to fit almost perfect from the top of the window to just barely touching the bottom inside rail. You can see both seams here:
After sewing the seams, she sewed in the glide tape as close to the top as she could.  She purchased the glide tape at Camping World.com.
To sew the glide tape in, she had to use a zipper foot so she could get close to the clips on the glide tape. 
Note that the spacing of the clips on the glide tape were not an exact fit for the curtains. Therefore, before sewing it in, layout the glide tape so you can center/place the clips where you want them.  We ended up cutting in between 2 clips to better line up a clip near each end of the curtains. 
For the center window, we are going to add a piece of Velcro so we can keep the curtains closed where the 2 meet in the center of the window.