Inserts have always been great for me. They worked great on my car in 1986 and still do -- I was just trying to see if the new stuff is better.
I believe Wagon windshield is same as sedan -- the roof-line is about an inch taller on the wagon though.
I have had mine not fit the windshield well either and I 'tuned' the metal ribs and has been great ever since. My ribs were bent too much away from the glass (the center touching and the ends curved up) -- this is the way they worked best on flat glass -- on a VW Bug for example. I have found on the ginormous MB Mono the opposite is best -- curve the metal ribs to just about match the glass curve.
Finally, no product on windsheild!!!! You want the rain water to 'sheet' and it does that best on pure clean glass. RainX is ****e and creates a zillion beads which refract and is a real problem at night. Not to mention is eventually makes a huge mess with the graphite impregnated wiper rubber such as Bosch. Even car wash wax can be a problem.
Keep it clean. Use Invisible Glass. Strip it with Acetone or smooth GoJo if you have to or even a glass stripper like this stuff **
http://www.amazon.com/Permatex-GS8-12-Touch-Glass-Stripper/dp/B000COBXFU ** if you have to. Results are great.
On side and rear windows I use Nu Finish wax as a bit off beading there can help.