As already mentioned I am having one of these currently being painted. How did you find the fitting. The glue and screws are supplied. Was the fit flawless or did it need some 'gentle encouragement'!? I assume you glued first and then put in the screws for the wheel arches?
being fibreglass there was a little adjustment to get it fitting properly, but not much, i had to file the curved area under the fog lights to get it sitting right, (the radius of the curve wasn't quite 100%) and had to slightly trim the black plastic under the stock bumper by the wheel arch on one side.
to fit, when the spoiler is fitting properly, i put the (self drilling) screws in to make sure everything lined up, then painted it. when it was final fitted, i put the glue in first, fitting it from the front under the grille, then popping the sides in place. the screws then were easy to put in the holes already there from the trial fit.
its easier to have 2 people, (i did for the trial fit) but i managed final fit myself no problems.
it shouldn't be difficult to line up, if its not right, stop, and check to see why its not working, the spoiler is very good, so achieving an excellent fit is easy.
oh yeah, be careful with the glue, its VERY messy, and likes to squidge out.. meths does take it off, but be very careful with meths on new paintwork, it likes to dissolve it!
i put my beads of glue quite low on the spoiler sides, (there is a smooth ridge for the glue on the inside of the spoiler sides) so it didn't squidge out so much.