While looking at HH options, I see they usually have a #1 and #2 size option - with the #2 usually specified for the Survivor, Explorer, etc.
For the Undercover, the site says, Survivor (XL). That makes me think the regular (#1) undercover might work with the regular Survivor and the #2 undercover is for an "XL" size. But I don't see any "XL" size option when ordering the survivor.
I'm sure a call the Hennessy would clear this up but I have a #1 undercover with an expedition and I'm wondering if anyone has tried that with the regular Survivor. I won't be putting a quilt in it - just a foam or thermarest pad.