The smaller the tweeter, the less important it is to put them on axis, but (typically) they won't play as low as a larger tweeter. I have a MK6 Golf, and some of those came with a Fender Audio package that has OEM A-pillar tweeters, does the MK7 have any different stereo options that you could source panels from that would eliminate the need to do any fabrication, and open up options for different sized tweeters?