installing pedestal seat mounts in a G3 1448lw

I bought a seat pedestal mount and swivel post from wal mart. How am I supossed to mount this from the bottom if my back bench in my G3 goes all the way to the floor and is filled with foam? What are my options at this point. I would also like to install a pedestal seat up front, but because of the livewell in the middle of the front bench, I'm going to have to add a steel plate to the aluminum ribs on the floor and then install the seat pedestal in front of the bench. What are my options with the back bench pedestal seat install???

some guys have cut an access panel on the rear of the bench and removed the foam to install washers and nut/bolt to attach the seat base.
others will say just use screws i am a big guy 300lbs I wouldn't feel safe with just screws.

Redbug, hey man, you're in good company. I'm a 300lber myself, that's why I bought such a wide boat 48". I've never felt so safe standing up and walking around a jon boat before! I don't trust just screws either. My father has some sort of a special pneumatic rivet tool for such an occassion. I do like the idea you posed about cutting out an access panel. We'll see how it goes. I'll post some pics once I start adding stuff to my boat. I just bought it from the marina last week, and haven't had too much time to do anything to it. What size boat do you have redbug? any pics? You should've seen the little 8 footer I used all last summer. If you want to talk unsafe, you should see the pic of me in it with all my gear. It was like 33" wide.

well I run a 21ft triton glass boat. I do own 4 small tin boats out in southern Illinois. the biggest is a 15 ft lowe I haven't done any mods on them as they only get used 2 weeks a year the small one is also a 8' boat but I haven't fished out of it in years..

I used 6 large toggle bolts that self tightened underneath and they have remained super tight. I'm 6' and weigh 285 and these have never moved a millimeter, and I always use my posts to sit up. The pic of my boat is a little blurry, but you can see where I drilled the holes out for the middle bench ( had to scrape out some foam) As you can see in the pic, the rear seat was already done and mounted and carpeted, I also added 1/2 inch of wood across the bench for extra support, then added about 8-10 extra sturdy screws drilled around the perimeter of the wood to keep the wood tight into the bench. The wood was an option for me, if you have thick decking, you probably don't need wood, I just added it for support. The toggle bolts definitely worked for me bro! D.