As said above, is it the fork stopping it going higher or the brake caliper?
I found with mine, my Shimano long drops weren't the right shape and in fact an old 10 speed era Sram Force caliper worked best. That wasn't ideal either so in the end went with one of these:
Just put my VO's back on this week after summer. Reminded me how the front part of the guard past the front caliper shakes, especially when you take a hand off the bars. Need to give it extra support somehow or maybe try a daruma bolt and see if that hold's the guard stiffer to the fork.