Anyone using an MLD Spirit quilt (or similar) as an over quilt for colder temps?

I'm tossing around the idea of going after a synthetic quilt in the 45 degree range to use, not only in humid midatlantic summer, but also to bolster a cold weather sleep system. I can't sew, so I'm looking at MLD's Spirit 45 quilt.
Has anyone gone this route too? If so, what quilt/bag are you using under the over quilt? I'd love to know temp ratings of your over quilt and under quilt/bag and how cold you were able to take your sleep system down to. Also, what type of clothing were you using too?
It seems like an approach like this would make sense to, theoretically, make the best use of all your gear throughout the seasons. You get yourself a 32 degree down quilt a 45 degree synthetic quilt and together, or separately, you have a great setup throughout the year (at least for what one might encounter around here). That being said, I could also see how an over quilt could compromise the loft of a down quilt or bag underneath it, yes? Throw the whole thing in a bivy and it sounds awesome, but I'm sure I'm missing something.
I'd love to hear your opinion or experience with a set up like this.

Thanks all,
Adam