John, I'm the guy that started the movement toward the Hennessy's here. What chuck has related to you is pretty good advice. I will pass along my experiences to augment.
If you have a bag with a pocket on the back for a mattress, take that one. Big Agnes bags have that. (Ridiculous sounding name, great equipment.)
I use a 3/4 length pad; it is made of two Ridge rest pads taped together with duct tape (what else?) with about a 1/2" gap between the pads. This gap allows for easy folding. It is an elongated kite shape, wide at shoulders, narrow at head, narrows down towards feet.
I used the spare corners that were cut off as a doorstep. I re-taped them together into a rectangle, and it sits immediately below the entry/exit slit of the Hennessy. On REALLY cold nights - freezing - my feet get cold where my heels press down on the bag and compress the insulation. Then, I slip my doorstep under my feet.
I've used a self-inflating Thermo-Rest pad, and it is nice, but very bulky. To save space on a kayak, I roll up my closed cell foam pad, tie it tightly with a rope kept for that purpose, and tether it to my aft bungees as a paddle float. The same sleeping pad is also used to kneel on for loading & unloading operations. It is also an easy chair in camp. It is also a kneeling pad - placed ion a gentle incline for drainage - on which to take a sponge bath.
Chuckie is also right (AARRGGHH!! it hurts to say that twice) in that the cited hammock will leave you vulnerable to weather & bugs. Frankly, if you take it along, let someone else carry it for daytime lounging. You will not be comfortable sleeping in it. On bad nights it will rain on your bag, and blow away the warmth you are trying to harbor in your bag. On good nights, the dew will saturate your bag. I would not depend upon it for shelter, daytime lounging only.
Of course, I could be wrong this time. I have been before. But, I don't think so.