Symptom: Most NPCs show body parts through clothing.

Using HGEC with FCOM. No problems prior to patch rebuild.

Wondering 1. What may be the cause. 2. How do I get some underwear for the male models?

Not sure about the cause of your bug, but if you don't want to see naked men in your game, all you have to do is install the underwear versions of the models from your male body mod, which I assume you're using or your males should not be able to not have underwear by default. I'd presume you're also using Robert's Male Bodies since that's the only male body mod I know of, in which case, like most popular body mods, it should have a choice of nvde or non-nvde models in the download archive, and the readme should explain how to install the underwear versions.

For your other problem, I might suggest posting your mod list, if you're using other mods, with this sort of thing, it often helps to do that as people are more likely to be able to find out what might be causing the problem if they know what mods you're using and what your load order is.

What kind of clipping?

If you have activated "Robes show pants" in the bashed patch, deactivate it.

Thanks forli that was it.

Again thank you all so much for being kind and helpful. I'm learning a lot. Some of it I'm relearning.

I look forward to modding again and to Skyrim.