Yeah, many things to factor in as others have said. I reckon though, I can see at least a couple of problems/snags perhaps.
Your kilometres may vary but I think you have some easily solved issues. You didn't use the straps, you don't know the exact temp. and it was your first time.
I gave quilts up and went back to bags and have gone back to a quilt for weather above about 5 degrees because I bought the Cumulus 150 on a whim and a discount and now I am learning to like quilts. In fact I reckon that thing is really excellent.
For me, and others may be different, tkmmv - the straps are the key. Undone or not properly attached draughts will drive me up the wall. When you are cold and not wearing much you are far more sensitive to every temp. variation downwards I find.
I'm no spring chicken but I used the 150 (40-OF) Cumulus in 7- 8 degrees (accurate thermometer) on an XTherm mat (it was new so had to test it-may have skewed the results?) with no issues but I did put the elasticated straps on properly. I was pretty surprised to say the least. I don't think I felt a draught-remarkable!
Also I kept a quite breathable nylon windshirt handy (75gms) and slipped that over my very light baselayers (Rab Pulse hoody and the UL Uniqlo Heattech leggings) about two in the morning. Next time ensure the elasticated straps are attached
and well spaced and taut, I could not get this to happen on my other quilts but works a treat on the Cumulus, and buy yourself a wee thermometer. A proper one-it may have been far colder than you think. The forecast reading station may have been tens of kms away. They usually are here.
Lastly, first time in a quilt is a weird experience especially if you move at all.
Stick with it-I am still thinking of the 350 and eagerly waiting Mole's (
@Mole )appraisal if it ever get's cool.
Thirteen is easily within reach of the 350. Good thing is they are excellent quality so if you don't want it you can always flog it!
Bake (and tramp) on.