Going by Julian's thread at least, it looked like a lot of time custom fitting the brackets/tabs was necessary to get his "just right", so I imagine what you're experiencing is normal.
Things like this are difficult to offer any input on if a person isn't standing right there looking at the clearances, so I'd say just give it some time and either you or your fabricator will eventually have an AHA! moment and determine what is needed to make it work.
And out of curiosity, are you wanting functional guards meaning that metal would be your first preference, or is it mostly a visual standpoint you're operating from?
If it's more of a visual thing, what would be the chance of picking up a set of GTS smoked tail light covers and simply cutting out sections of those so that the remaining material would give you the look you want?