Hello Jay bee
The primitive world of violence has so many reflections to the rest of the animal kingdom, I've worked with a few blokes your size and a hell of a lot of women your size. My best advice is don't try and make up for you not being a lofty by over killing your attitude and aggression, nobs will just think you've got small mans syndrome and make you a target for piss take. You need to be like the lion mate, proud and confident, not splaying your arms out and being over agro to solve things.
The guys I've worked with often had more problems if they looked a bit poncy too, so try and look and feel the part. I'm not talking about waltzing about like you own the place, walk about like you don't give F*+K who owns the place but be nice and polite. People will always read you from your body language and your eyes a lot of the time. The only way many of these drunks and druggies will give you any respect is if they think you might be something that could test them BUT having said that many of them won't give two tosses how big you are, giving a doorman a dig earns them a great deal of kudos in their sad lives.
Second bit of advice, get yourself down borders and do a bit of research, i used to read a lot of Geoff thompson books years ago and although the job has changed a fair bit at least you would be going into it with your eyes a little more open. Someone mentioned about seeing if you would need to wear PPE like shin pads, my advice is, wear it all, especially a groin guard, shin pads and decent boots to stop you from twisting your ankle. Just take care of yourself, theres never any harm in asking for advice in a world where sometimes it can be the hardest thing to bring yourself to do.