Will this quilt work?

I think taking both would be overkill for those temps. Just bring an insulated jacket or something to wear around camp and wear it to sleep, much more efficient use of the weight. I've slept pretty comfortably down to 35 using a 45* bag and a synthetic jacket.

Of course, your mileage may vary.
With a good jacket, you could probably just take your 2.5 Apex quilt.

A 5oz Apex quilt should be good to 20 or so, from what I've read before I made mine. Lowest I've taken my 5.0 Apex quilt was about 38, but was so warm I didn't even have it closed up at the feet or tucked around me (wearing only boxers and in a tent, also, I'm a warm sleeper).

7.5oz Apex is going to be really bulky. You could seam rip some of your current quilt and add another layer of 2.5 to the body/legs area, and leave the sides that get tucked around you at 2.5 then resew. This'll give you warmth where you need it, but minimize weight and bulk.

Tim Marshall puts 6oz at 30f and 8oz at 20f.

I have a 50f 2.1oz apex and find it chilly at 50f.

Edit: to fix temp

Stephen, is the "5f" a typo?

Sounds like the 7.5oz will do the trick for keeping me warm. It should be interesting to see how bulky it turns out. I have never ran into any problems with my homemade pack. It has some serious room and I just pack my sleeping bag/pack loosely bagged whenever I hike.

Yep Justin, its a typo, it should be 50f

I just made a 2.5oz quilt with leftovers from another project. I also had some 5oz and considered making a Vireo-style quilt with 5oz from the waist down and 2.5oz from the waist up. That way the bottom would be good on its own down to around freezing and the top would be good to about 45*. When it gets down into the 30's I always have an insulating top with me and would wear that to bed to boost the temperature of the top half of the bag. It sounded good in theory but in the end I was seduced by the low weight of an all 2.5oz quilt and went that route. However, the different insulations on top and bottom might be an effective way for you to use your leftovers and keep the cost down.

I never pushed my 5oz bag to its lower limit but from the reports I've seen and Tim's temp ratings, I'd think a 5oz quilt would replace your TNF bag and adding some warm clothes and a hat should get you down to 30*. 7.5oz sounds like overkill and really, really bulky. Personally, I'm happy with synthetic insulation for anything over freezing but for below I prefer down for the smaller packed size.

Adam

I ended up being weather conservative and making a 7.5 oz quilt (6ft. by 4ft.). The weight came in at 29 oz (which tells me climashield is a little heavier than advertised).

It all came down to me being really worried about my thin FLA blood.