Should not be a problem, and the age old adage is that homebuilts and antiques are NEVER turned away, regardless of the advertised capacity status.
 
We never turn homebuilts away, we will always find a space, somewhere. May not be a prime spot but it will be at Oshkosh.
With the additional space we’ve gained over the last few years we haven’t come within spitting distance of filling up, even though we inch closer to that point every year.
 
How far from the homebuilt pavilion am I likely to be parked if I arrive Saturday evening?
If you arrive the evening of Saturday the 27th you will likely be pretty much right next to the pavilion in a recently vacated spot. But the evening of Saturday the 20th - probably much farther away.
 
Oshkosh 2025
I’m looking at camping here in the HBC area (red square area in photo).
I can arrive any time the week before and will most likely do some volunteer work.
Not sure if you are dictated where to park or can just taxi on over to that area?

Oshkosh Camping Location.jpg
 
I'm sure the early birds will be along to tell ya more... in the past you'd have your HBC sign and then a second one with a numbered section you'd like.

An opion you didn't ask for: That spot you've selected is furthest from the pavilion and the better showers/toliets. Could be intentional.
 
Oshkosh 2025
I’m looking at camping here in the HBC area (red square area in photo).
I can arrive any time the week before and will most likely do some volunteer work.
Not sure if you are dictated where to park or can just taxi on over to that area?

View attachment 73903
Typically, I don’t think the HBC volunteers doing parking are there prior to the Friday before the show. The area you marked has had camping in the past. The only risk may be if you park differently than the HBC team expected, you may have to move to accommodate their standard. The burn lines will be there, so the risk should be low.