If you got good seeds from someone, (and if you are a GVGO member I'm sure you did) it doesn't matter how big your tomato is you can keep seeds and the genetics will be there.
I was talking to a friend today and he was using the fermentation method to save seeds.
That works okay but there are easier methods.
I use the trisodium phosphate....what!
I think John Butler uses the same process but uses Oxiclean instead of TSP.
I don't store mine in the freezer but i do put them in there for a week. Somebody told me you should do that so the seeds have been through winter. Is it necessary, I don't know. I do know that it doesn't hurt anything.
I rarely have a seed that doesn't germinate
Spread them out on a paper plate and let them dry for a couple days.
Put them on a paper towel and spread them out to dry them a bit
Rinse them in cold water
Scoop all your seeds and put them in. Let them sit for 1 hour and all the gel will be gone off the seeds
Sounds pretty fancy but it's pretty common and most people have it. You can buy anyplace that sell paint and it's not expensive.
Mix 1 tbsp. in a cup of warm water.