I'd bear in mind that security issues revolve as much around the likelihood of your being a possible target for blackmail as any other matter. So, to have any skeletons in your closet is a bad thing. Also, things have tightened up in this respect a lot recently, just be careful you don't end up walking a one-way street to unemployment...
Sorry to be vague, but I get uncomfortable when security vetting is discussed here. My advice, if you haven't yet got the licence, is to pursue another career - but that would be my advice to you anyway!!!
AD