Depending on where you read, some say replace the stringers one at a time, other restos I have came across have removed them all at the same time. I was really apprehensive about cutting them out all together, but the floor is really solid. The "foam" secondary stringer was only held in with CSM and the primary was pretty much just the fiberglass cloth shell. That helped me make my decision--not much strength/reinforcement there anyway. It may also help that the floor had previously been replaced and there is extra cloth on the floor, I do not know for sure.
The sawsall ripped through the primary stringer like it was nothing. There was about a 30 inch section near the transom where I cut through solid wood (at the hull, rotten near top). I also bought an oscillating multi-tool that worked really well cutting the skin off the transom and cutting out the foam stringer. Maybe I will be able to work this week on the other side. I post some more pictures when I finish cutting the other stringers out.
Just a side note...wear long sleeves and gloves when you do your fiberglass cutting/grinding. I bought me a Tyvek suit today.