If one were to cut trousers to sit at natural waist and not want suspenders or belt, is there another way to adjust the waistband to cater for small fluctuations in waist girth?
The problem is that cloth is not so elastic. Â If you want it to contract, it has to bunch up somewhere. Â If you want to expand ... well, it can't, really. Â There are trousers made with an elastic strip hidden in the waistband, sort of an "interior belt" with ends that peek out at about the mid-point on each side, and button on the waistband. Â By changing where they button, you can adjust the fit, a little. Â It works reasonably well, but it's not great.
Alias mentioned sidetabs. Â What are they, and do they work?
Two little straps of cloth, joined togehter by a metal buckle. Â Some place them just below the waistband, others so that they straddle the waistband seam. Â When you tighten the tabs, they scrunch the trouser waist together at the sides. Flusser uses these religiously. Â Nearly all of my Flusser trousers have them. Â I find they work about as well as the trousers fit in the first place. Â If the trousers fit snuggly in the waist, the tabs are great, but not really needed. Â If the trousers are loose, the tabs are needed, but they cause an unsightly bunching. Â Also, the more you cinch them, the less comfortable your trousers are. Â Personally, I hate the whole principle of cinching (whether through tabs or belts) for keeping trousers up. Â It's a form of self torture. Â I consider the tabs decoration (a nice one.) and wear suspenders.
Do beltless and suspenderless pants look weird? Â Does that contravene any rules?
No, they have been around for a long time and are part of the canon. Â Leaving aside, of course, robin's egg blue Sansabelt polyester golf pants. Â Those are definitely against the rules.