size will always be a factor. However, it can become less of a factor as skill levels become further separated. I'm a big guy too, but let's assume I'm little, and I am not very skilled. You would most likely eat my lunch. Now, let's assume that I start fighting, gain more experience, etc. and you do not. Now, your size is less of a factor. It's still a factor for sure, but skill can compensate somewhat.
The problem here is what we define as skill. you said specifically, "Can a smaller guy who has more experience in forms and such successfully defend himself against a guy who is bigger in size and strength?" No, someone more experienced with forms may not be able to. Someone smaller with more fighting experience though? sure. You are a big guy who boxed - can you take out de la hoya? How about mayorga? Hopkins?
i'm nobody...i'm nobody. i'm a tramp, a bum, a hobo... a boxcar and a jug of wine... but i'm a straight razor if you get to close to me.
-Charles Manson
I will punch, kick, choke, throw or joint manipulate any nationality equally without predjudice.
- Shonie Carter