In response to yet another problem for which the solution is invisible targets that no-one can find (logical, I suppose), I'm feeling bound to offer my part-solution.
I am terming these 'null' targets because, as they stand at present, they are not invisible, they are merely not obvious.
Please give 'em a go. If they meet the functional need I don't think it's a big jump to get them to the next, and maybe final, level. Though I will need a leg-up.
Happy DoFiring . . .