Have you ever tried a double front layer tee Janet? I used to have one but haven't found one again, though I'm pretty sure I've seen some advertised so I'll have to look around as I could use one myself. The second layer in the one mentioned was only on the front so it wasn't as hot as having a full second layer, or wearing a tighter cami (something I simply won't do).
I'd also like to find a tank with this design (double layer in front only).