Whats the best way to adjust the parallax on a 3x18x50 scope? My zero is 200yds @ 14 X. Parallax is perfect. I know parallax changes with power changes. Would it be better to set parallax at 18X, and just leave it there? Using the 200yd zero. Scope will be used 90% at 14X. Occasionally bumped up to 18X for a whistle-pig at 400yrds.