At the expenss of fitness and power, don't try to force the weight off your body fight were you are natural.

Unless you are technically brilliant going into your first bout you won't have any advantage at that height and weight... you'll fight some short kid who's as strong as an oxe compared you you and becaue he hasn't burned off all of his energy stores hel'll just come tearning into you.

I've seen hundrens of tall thin lads get beaten by short people in their first fights because they don't have the skills to box them properly because they are too inexperienced.

You won't have the same amount of power because your arms are longer so you'll loose power in your shots from throwing them more than some one with shorter arms compared to their weight.

I'm not saying you need to bulk up like a body builder, but 11.5 stone at your height would be too skinny to be fit or healthy.