old boards vs new

I have been trying to think about why my old boards were so different than my new boards. I used to think it was just because the new boards have more fins but really it is more complex than that. My old boards had a simple bottom design, a mostly continuous rocker except not so much at the tail as my newer boards have, they were mostly flat with maybe a very slight concave in the midsection and a marked V at the tail. So the tail might have a flat area but it also had a strong V. The rails seemed quite similar. I used to ask for very hard rails that I heard later were called China rails but still similar. The outlines were similar but a little longer. My new boards have concaves on the bottom and no V. In my imagination this gives the board more push but also makes it not want to dig into the wave and carve on a turn. V bottoms carve into the wave so the harder you push the deeper it carves but concaves push the water away and give the board lift so you can carve but it's not the same since the board wants to stay above the water but with multiple fins it holds it somewhat into the water. Well anyway that is what I think for now but I can still jam a hard bottom turn without popping the fins out. I can also push the tail and make the fins slide something that you couldn't do with the older single fin boards. I used to pop my old single fin out above the lip in a maneuver that appeared to be different from the fin popping maneuver everyone does these days. It was more similar to a skateboard grind maneuver where I would be sliding sideways along the lip of the wave till I made the fin engage again. Perhaps much of the difference is that I am an oldmanoverweightoutofshape and I am surfing a board made for me. 
