The bump stops are really the best ways to approach this issue. As pointed out earlier in this thread, longer adjuster bolts in the factory location will bend/warp the grille assembly even more than than the factory bolt. Remember that vacuum is constantly on the system, so unwanted forces are always being placed on the grille assembly. The bump stops spread the vacuum forces to multiple areas decreasing the warping. See the link below, it shows what I used to make my bump stops. Within the link below there is another link showing the stops installed on my convertible project.
Steven