Hi Matthew, sorry for the late reply but I have been working out of the shop this week. I've never removed one from a 25/30, but I would assume it is much the same as other coachbuilt cars of the era. There will likely be trim panels all around the sides that hide where the liner is tacked to wood trim around the roof perimeter. Then there may be either steel rods that spring from side to side that slide through loops in the liner, or the liner could be nailed to wooden bows that go from side to side. The wood trim around the inside of the rear window will most likely need removing, and possibly the windscreen trim too. Just start carefully removing trim around the perimeter and you should find your way. There could likely also be trim pieces that are a mystery how they are attached, they may have tacks embedded in the substrate under the trim upholstery that can be very difficult to remove without damage. If you can post some pictures of the interior I may be able to advise you better.