I dare not take the 'string' test. I am short, and even within that, have exceedingly short legs for my height. Most of these things work only for people who are average in intrinsic proportions.
I'm a bit over the 25, but have leg muscles that are substantial, a large ribcage and thick bones (on the usual bone tests I come out as well into 'large frame' for my height, and I pay a woodwind instrument, and have a pretty decent lung capacity..).
I have actually found Vorpal's posts here very illuminating. I'm very keen on proper evidence, and it's been evident to me for some time that the BMI measure is not fit for purpose. I do have, on the 'wobble test', a few little bits I could do without, and am remedying that at the moment- I'd like to be about 1/2 a stone to a stone lighter, but increase my muscles, which past experience suggests is my best and healthiest situation. My problem is not that I eat too much, or eat the wrong things, but that I work at home so I have to actively get out there to get much exercise, and other things than work are getting in the way (house move looming, relatives needing more care).
The most weight I ever lost in a short time was 3/4 of a stone in under a week. This was due to extreme stress, when in a truly awful hospital. I can easily lose a pound or two if I have a very stressful day even now, and no, it's not dehydration or starvation, I just seem to develop a (temporarily) fearsome metabolic rate. I seriously don't recommend that way of losing weight. You do not feel good for some time after, it cannot be good for a person. It makes me very concerned about drugs which try to set this sort of reaction off.