Having seen both 40+ size nitro high wingers and simpler (less than 50 inch) wingspan foam planes in the hands of beginners, it always feels like the bulky nitro high wingers offer much more stability for beginners (especially absolute beginners, and particularly when they are on a buddy cable).

So should beginners be building larger foamies, so that they are more stable ?

The problem in many cases is really building exactly as per down loaded plans.
You are right  many build  exactly as per the tiled plans available on the net without understanding that  the location at which these planes are flown is possibly a backyard or a  park  and then take the same plane to a flying field and try to fly it there  the vast open space of a flying field  has very different wind and ground effect  as compared to a park.

So a bit of understanding and imagination is essential  to scale up the plans should you be looking at flying at a flying field.
sai

In my case, I did download the design that was for about 34inch. I printed the pdf at 140 percent and that gives me a wingspan of about 48inch.

However, in addition to what Sai says, I feel that it may also have some bearing with the power system that people already have and back calculate the wt require hence the size...

Pankaj

no not really a model up to a max 30inch wing span can be flown in a medium size ground 

where can i get coroplast sheets for making rc plane in kolkata?

Kindly check last post date before posting ! N your question is in wrong section ! Try the wanted  section !

I think it all depends on the size of the plane a person feels comfortable with.....Big sized planes may be intimidating to beginners when flying solo...

Yes, stability wise big planes are best...

I learnt flying on 40 size plane but under an experienced trainer who always provided me the support....I knew he was there to take care of in case of mishaps...so the size of the plane was not intimidating....

But for practicing alone I felt comfortable with my scratchbuilt Mini Avispad.....

But now I enjoy flying bigger planes....