So, I made a top quilt. So far so good. Looks great and thank you to everyone on hammokforums who posted their DIY TQ journey (w/ pictures and/or video before!)
A special shout out to James from Little Shop of Hammocks for a great experience buying the fabric, No-See-Um baffle material and such! If you're in Canada, go have a look at his site (and listen to the Hang Your Own Hang podcast episode where they interview him).

Anyway back to the actual topic/question.

I was nice and toasty for the half hour I tried it out before closing it up today. It was ~26.5F / -3C outside.

I used the spreadsheet from the forums here and I know about the loft ratings and such (it came out to about 3.5" loft on average I would say). The problem I think I might have (or not) is that I do not know what kind of down I have. I had the idea to make the TQ because the SO was gonna throw out an old IKEA down pillow. It says 90% duck down 10% duck feathers and has about 900g of fill in it. I think I got quite a bit of that to go into the TQ (instead of flying about the garage - shop vac method rules if you ask me!). I used an analog kitchen scale and got about 40-50g of down into each baffle.

Does any of that matter or can I just go by the loft, i.e. 3.5" means I get about 10F / -12C out of this and it weighs whatever it weighs? Any tips for figuring out how far down I can use this without killing myself?