Maybe I am missing something but my bare hi-loft has stretch panels in the knees and in other places as well. Sounds like a possible fit issue or someone is confusing the bare hi-loft with the bare 200 gram thinsulate suit that isn't of the hi-loft variety. The hi-loft variety is in fact thicker than 200grams, is a hi-loft garment, and is also thinsulate so I doubt if it is much less warm than the diving concepts brand mentioned above at 200 grams. The hi-loft is comparable to the dui 400 gram and the weezle but it's much cheaper at LP. In fact, I prefer it as those two (dui and weezle) come with there own issues like plugging the dump valve on my shoulder with soft fabric but that's for another thread.
Chreamofwheat...good luck.
The answer is that you are small and the water is cold. Moreover, Men are natural energy factories and tend to have more muscle and fat/size than most woman and this increases warmth. In addition, judging from your post above, you probably aren't using dry gloves and maybe need a better hood if your hands and head are frozen solid after only 15 minutes. The bare undies have nothing to do with this problem. If your extremities are cold, then you will likely feel colder than you really may be. Again, that's natural in cold water and no dry suit or any undies out there will help that for some people or any person given an extended dive
It's a dry suit, not a warm suit and I always feel that it's somewhat of a fallacy when people say that they are much warmer in a dry suit than in a wet suit. Yes, it's mostly true, but the water is still 40 degrees. The dry suit only slows the inevitable.
I also get cold easily and I have waisted money and time on multiple pairs of undies. The best thing you can do is get dry gloves and maybe a better hood. That may help a bit. And still, the water will be cold and you will be thin/small.
People always use the word "toasty" here on SB to describe how they feel in their dry suits. I have never felt "toasty" warm in my dry suit and most of the people I dive with don't feel "toasty" warm in a dry suit. Toasty warm is the feeling I get when I sit in front of a fire and not at the end of a 1 hour dive in 40 degree water.
People are different when it comes to tolerance for cold and one's body/etc... plays a huge role in this.
Good luck!