The major issues you're going to have with that setup are three fold:
1) The width of the quilt, doesn't lend itself to really blocking drafts, it'll be difficult to get really effective and consistent tuck, especially with all the down gear adding bulk to your profile. (don't get me wrong, a 52" wide quilt with a half-taper should be sufficient for most people without the down gear making you a marshmallow)
2) The quilt is unbaffled, and as such, is highly susceptible to another form of drafting, even if tucking isn't an issue; seam-draft. It's not really drafting per say, it's a thinned cross-section of marginal or no-insulation where the thru-stitching separates the down chambers. Not really an issue with down gear, but when stationary at resting rates, it's a big issue.
3) The lack of using a bivy; if you did use a bivy, you'd go a long way to eliminate those drafting concerns, but since you're not, you've no protection from this issue. It may seem like I'm overstating the drafting concern, but once you spend some time in bonechilling temps with high winds, you'll know what I'm talking about.
Personally, I'd say your summer quilt would be a great addition to any other bag or quilt (on top of it) to augment temperature, but with no baffled gear in the mix, you're going to have a very hard time pushing the numbers. That's why I prefer to make even summer quilts (40+ deg) baffled, the weight difference is marginal (0.5oz or less when linear shrinkage is factored), and even though the manufacturing difficulty is increased, the versatility is infinitely higher.
Pushing an unbaffled summer quilt just isn't ideal IMHO, better to push a 3-season quilt or bag.