Early A carpets.....

Attempting to install a set of replacement carpets in my '65 Valiant 2 door post car. The carpets that came out of the car were a custom fit, 1 piece set of loop pile that were 100% glued to the padding and that was 100% glued to the floor. Long story short, they got destroyed getting them out of the car due to dry rot as much as the ubber glue job. So, I have a two piece set from a reputable aftermarket supplier and am not happy with the fit around the transmission tunnel. They are loose to say the least. Can anything be done (heat gun or steam) to tighten up the fit or do I have to live with it? Does the front section overlap the rear section or the other way around? The set has jute felt insulation/padding bonded to the back side.
Bob