Does anyone have experience with an above floor radiant system consisting of 2x4 sleepers with a mud pack in-fill?

We purchased a house out of bankruptcy with the subfllor and interior framing already installed. The price of panel systems is simply too much for our budget. This seems like a reasonable comprimise. I assume the responsiveness will be a little worse than gypcrete given the density of the mud. This maybe offset slightly by thermal mass that will keep the floor warm during the day when the heat requirement will be low.

The house will be 40% tile, 60% hardwood. the tile areas will be 100% mudpack, no sleepers. The price for this is less than $1 square foot versus $3+ sqft for quiktrak or thermalboard.

Opinions?

No experience but be sure to ask the following questions: Was the floor designed for the weight you propose? What will be the impact on your doorways, ceiling height, height of various cabinets, recepticles, windows, plumbing etc?