My two-layer Hennessy hammock has a removeable open-cell foam pad fitted between the layers that provides warmth down to about 55F. I am camping this weekend where the temps will be dropping potentially below freezing.

I have an underquilt rated down to about 20F which I will definitely be using. My question is...will I be warmer if I remove the foam pad or if I use it in conjunction with the underquilt?

More insulation equals more warmth, unless I'm missing something.

Unas10: "More insulation equals more warmth, unless I'm missing something."

That's what I thought too but was advised to remove it by Jacks R Better (where I purchased it). Their answer isn't sitting well with me; thus, I'm reaching out to the specialists here.

Neither a specialist, nor do I play one on YouTube.
I'd use both, Argo. I use both a pad (new one is R 5.4) and an underquilt if under 40 (I am a cold sleeper).

I don't understand why you'd remove the pad unless perhaps it pushes against the down in the underquilt and somehow compresses it creating cold spots, but you can easily test that before you go. I'd take them both, and if for some reason the pad is causing a problem, just remove it.

Use both the pad underneath and the underquilt. Just a few tips for you. You should pitch your tarp at a steeper angle and also close off the ends like a set doors. Keep the tarp tight to the ground everywhere to stop the wind and heat loss. Sleep in a set of polyester long johns. Find a location that is protected by trees or bushes to cut down on the wind. Eat a good meal at dinner, your body will be like a furnace burning off that food. Wear a wool cap to bed. Last tip is fill a flat rubber water bottle with hot water when you go to bed, Position it under your legs.

You never stated what your sleeping bag or overquilt is rated for. Better make sure your bag or quilt is rated to the lowest temp anticipated.

Agree with the take and use both. I use both pad and under quilt all seasons as the pad provides support and I can loosen the quilt in warmer weather.
Also consider that heat rises. I use a poncho liner draped over the ridgeline when below 40 to create a cocoon effect.

I find an underquilt protector helps cut any wind to help the underquilt retain heat. Jiminy finds its very comfortable as well.

Thanks for all of your advice.

Fortunately, although a bit below freezing, it was dead calm but I like the poncho idea. I have a fleece liner that I climb into and then using my -10 C bag as an overquilt with a foot box. I also wore a fleece hat and socks. No long-Johns.

The terrain in the French River isn't particularly hammock friendly and our site has no soil for stakes. Very shieldy. It's all about attaching the tarp tie-outs to rocks. Not particularly fun for making adjustments.

The first night got down to -3 C. No problem. I am normally a warm sleeper though. I don't think Mrs. Argo would enjoy these temps. But there's always those pee breaks that interrupt the experience