Kodak Portra 400

Hi Terry. Are you weighing down the strip from the bottom as it dries? I would drop them in some distilled water and try again. I'm not sure about heat. If they dry in very low humidity, the emulsion side will dry faster, causing them to curl inward.

Four wooden clothes pins on the bottom. I had a really hard time getting them into the film holder on my Epson 550. Low humidity,
Next time I’ll run hot water in the shower for awhile before hanging.

That’s a good idea. I have an Epson. I threw the film holders away. Those things drove me nuts. I now use the wet scan holder plus a piece of anti-newton ring glass. Hardly ever wet-scan, but the holder is useful.

When you say "curly" do you mean from top to bottom (like it is trying to re-roll its self on the spool), or side to side (commonly referred to as "cupping")?
Some films just like to keep their shape. there Are special weighted clips you can buy that will help with curling. Cupping on the other hand, is a different challenge altogether. Smooshing between heavy books does help to a large degree, but doesn't 100% fix the issue.

Some cupping, but primarily rolling into a tight ball.