Different manufacturers size their frames differently. In my bike shed I have 3 frames- a 15" bianchi, a 17" kona and a Large/medium Tandem. All 3 bikes fit me perfectly- including the 2 sizes on the Tandem. The only thing to do is try the bikes and find one that fits you. I even ride a 19" kona, with the saddle right forward and a shorter stem so even "Wrongly" sized frames can be improved. On the weight thingy- Any modern frame will be able to take that weight. What may not are items like seat stems on the Lightweight bikes and wheels may cause a problem on some of the cheaper bikes. Only mod for weight that I would suggest is wider tyres to add a little more comfort.
Incidentally, I am 5'6" short and a 29" inside leg.
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How long was I in the army? Five foot seven.
Spike Milligan