Loc: Central Texas
Yes, and I like it. It is a great way to salvage a tent that has lived past its use-by date. I even put garter hooks inside a tent to clamp the groundsheet in place - not worth the weight or trouble. However, putting a groundsheet inside the tent is not the lightest system. Replacing the existing floor with silnylon is probably a better bet, IMHO, but a lot more trouble.
Loc: Kitsap Peninsula, WA
I have used tents with floors and without. I see advantages in no floor. I use a light plastic paint tarp (as light as half mil) and secure the corners with rocks. I then wrap the floor up the sides of the tent a bit to keep out insects and water. So why do you need the extra weight of an untreated floor? The only advantage of a sewn in floor, as I see it, is when it is bathtub like and keeps out water that way.