I'll think you'll be happy you ditched the Razor--fleece isn't a good material for a sleeping bag, IMO--far too heavy for the insulation value.
In fact, any double-layered sleep system where both layers are only used for sleeping will be inefficient, because you have twice as much (non-insulating) fabric as you need. This isn't trivial, especially with warmer temp bags or quilts, where the ratio of fabric to insulation is already high. For example, the shell fabric on my GoLite 1+ season quilt accounts for more than half the weight of the whole quilt (granted, there are similar quilts with the same amount of down and significantly lighter fabrics).
If you want to go with a double-layered system, consider carrying down or synthetic insulated jacket and pants, and wearing those to sleep in on cold nights (inside your quilt). This is a very common tactic around here. That way, your second layer is multi-use, and can also be used for camp. This may allow you to replace insulating jacket and pants you were already carrying for more weight savings--for example, I have a Montbell Down Inner jacket (6.5 oz) that replaced a fleece weighing twice as much, and is warmer. It is also much more compact, which means a smaller pack volume needed. The caveat is fleece is far cheaper, breaths better if you wear it while hiking, and manages getting wet much better than either down or synthetic puffy layers.
The location and length of your planned thru is also huge (but then, you know that). I can make a 35F-40F quilt work for me in NW mountains in the summer and three seasons at lower elevations (also in the West), but that's supplementing with a down jacket, being careful with site selection, and willing to deal with a cold night or two. And I sleep warm.
As I mentioned up-thread, you've been carrying a very heavy bag for the warmth on your previous hikes, so there's no reason your weight should go up when you prepare for colder temps. Just think of all your gear as working in systems, not as single pieces (for example, a tent stake is a much better substitute for trowel than a bottle cap--and you're carrying them anyway).