Doug5150

The chart is not gospel, it's just a general guideline. As long as the tire sidewalls are wider than the edges of the rim, you'll be okay.

Narrower tires are also not as tall as wide tires so there's always an increased risk of pinch flats with going to narrower tires, you just need to be more careful with hitting edges with the wheels. I weigh twice as much as you and I used 1" tires on a bike for a while, and had no problems. I took them off because they rode harsh, not because they failed at all.

The Matrix 750 rims seem to be a pretty inexpensive rim, by the by. Google finds a lot of comments about how easy they are to knock out of true, but the difference between a 28mm and a 25mm tire won't have much effect on that either way.
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Since the rims are rather inexpensive, I would check what the rim's max pressures are. Tires have max inflation pressures molded on them, but rims have maximum inflation pressures they are rated for as well and the pressure varies with the width of the tire (narrower tires can be inflated higher).

I found one mention that seems to indicate that the Matrix 750 were manufactured by Bontrager, but they no longer appear on the Bontrager website, and I can't find any manufacturer info for them anywhere. They may be a 2007 or low-end OEM model not listed so you would need to email Bontrager and ask. Alternately, lots of current Trek bikes seem to use the Matrix rims (as well as Bontrager tires) so you could try emailing Trek and asking what the rim's tire/pressure specs are also.
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