Exactly what they said, OP.

No need for the fire suit here. I much prefer aluminum for a touring bike too. Steel really is squirmy with a load. Some is better than others, but aluminum significantly is better. I plan to have a custom bike built in a couple years and am specifically keeping an eye out for builders who work in aluminum. I very regularly stand when riding, but my original early 90s Trek touring bike flexed so badly it kept me seated much of the time when climbing, accelerating, or descending quickly on winding roads. I got an aluminum frame-set and it was a night and day difference. It handled a lot better and felt more stable in general, presumably partially due to not flexing so much. There are a lot of 90s aluminum mountain bikes out there for cheap that everything from the current build could be swapped onto. Just a thought

The weight being low and forward advice is spot on too. Stand all you want, it’s no big deal. Put the weight up on a rack hanging out the back of the bike and it’ll toss you all over in comparison.