after throwing together my first homemade 10' shotgun rail (2x1.5" sched 40 pvc screwed to a 2x4 with 3 T-braces for legs/feet), i thought i'd share my experience after checkin out a bunch of these threads and coming across the drill from the top or bottom debate a bunch of times...
first and foremost, liquid nails is about as useful as a poopy popsicle (maybe cuz it was 10 degrees last night, not sure if that effect's the tack from setting)
***more importantly, JUST DRILL FROM THE TOP. after a slip up or two on the first two holes ("that's what she said"), we quickly discovered to bore a very small hole in the top of the pvc with a tiny drill bit (or score it with a nail or something), that way your larger drill bit (if you have cheap powertools like us) can grip the top of the pvc and bore a nice smooth larger hole. once the large holes were drilled, we just drilled in 3" weatherized screws down through the bottom of the pvc and into the 2x. since our ghetto drill lacked a long drillbit, we used a screwdriver to fasten them super tight. put 1 screw in each pipe (side by side) in four somewhat evenly spaced intervals down the pvc, and the pipes are locked down like a cuckold husband
didn't even have to sand the holes in the top of the pvc. just took my skis and slid them down the pvc a couple times, put my boots on, threw the newly built rail outside and it slid like a dream
once we got rolling, all in all it took about 30 minutes to build, and with scrap wood cost us nothing but the price of two 10' 1.5" pvc pipes (roughly $6 at home depot)... meaning if you haven't built one yet, just do it. so easy a first grader could make it and a second grader could afford it