Gotcha. Yup, my quads are definitely dominant as I started off doing seated leg presses for a few months before learning what it was I should have been doing the whole time...
As a substitute for GHRs, would (I don't know the actual names) the laying-on-your-stomach ham curls and the seated-upright ham curls work, even though they're somewhat isolating moves? Don't have a GHR machine, and the one option I have to rig up is to place a flat bench next to one end of the cable crossover rack (don't know the name for that one either but I think you know what I'm referring to), and lower the pulley and hope my ankles can get under the pulley mechanism..