If all else fails, you will have to take the seat apart. You might be able to pull the seat cover somewhat off from front of seat, when sitting on seat, the springs will be compressed so that the cover material should slide down and out of the frame slot. Then you will be able to see the front hold down bolts thru the springs I think you will not have to take off the seat pad, should be able to see under it. Should be able to use a socket on bolts (10MM). Then for the rear hold down bolts, you said you can feel them, so you will need a 10mm closed end wench for them. I suggest a 10mm Gear Wench for this. Let me know if this helps.
Bob