How many walkons can your team have without impacting player development, etc. It seems that in the WIS documentation I've seen 1 and 2 thrown out. Which is correct?

No more than 2.

you can definitely have one walkon and no impact.

the official word is that there is some negative impact on player development that starts with the second walkon.

but i have seen respectected coaches post here that say the negative impact with 2 walkons is minor and not worth worrying  about.   some have even said that a third walkon does not hurt too much (but definitely noticeable)  and then it ramps up form there.

That's what I thought - thanks.

Even with three walk-ons, the penalty you exact for having those walk-ons is almost always negated by the increased playing time for the scholarship players you do have.  I wouldn't sweat three a bit.