This is my first cold weather cycling season. In years past, I was on the trainer anywhere below 50F. This morning at 5:45 AM it was 32 with a windchill of 27. I would've been warmer in daylight at this temp due to sunshine but I ride every morning 30-45 min before work.
I won't get into my full kit because I was fine except for my gloves, which are being addressed already, and my groin & knees.
I wore some Descent thermal bib tights. They're fairly thick and wind was not a problem. My thighs and calves were great. My groin and lower abdomen was cold and my knees were cool, not quite cold. I had only this single layer.
Things I could do right now:
- Underwear baselayer, and deal with the bunching of material
- Liner cycling shorts baselayer, which have a chamois. Two chamois does not seem like a good idea.
- Sweat pants over my tights. I've walked the dog in sweats before and I doubt they will do a whole lot, but it would be something.
I'm not familiar with the bib tights you cite. For cold weather riding, I'll go with normal bib shorts and tights specific to the weather. I've got three levels of tights: the cheap poly down to 40F; a heavier, lined pair down to 30F; and fleece "tights" (that really are loose) below 30F.
Another pair of tights with chamois is probably the most expensive thing I can do, especially if they are bibs. I think what I have is probably similar to what you're wearing down to 30F. I wasn't miserable, but my groin in particular was cold enough that it was distracting.
Are you layering above or beneath, or wearing just the tights?
My tights have no chamois, and they usually go on sale (Perf-bar) for $30 a couple times a year. Normal bib shorts with chamois underneath, tights on top. One layer on the knees, two on the groin; adjust the weight of the tights to the weather.