Center Eligible
 

Playing 8-man Flag, is the following formation legal and is the center able to be considered eligible? We don't have eligible/ineligible numbers.

()
OXXX O
OO
O

Here we want the O's to be eligible receivers and X's are line and ineligible.

Also, a NFHS reference would be appreciated if you can, thanks!

Any player on the end of the line is eligible. Same applies to 9, 8 and 6 player football. Only difference between 11 player and the others is that there aren't numbering restrictions. You'll find the rule in the 8 player rule differences section (Rule 7c).

Does flag play NFHS rules?

The "center" is never eligible as he is always the middle of the line and is covered up every play. Having said that, I assume you mean to ask if the "snapper" can be eligible. Under 11-man NFHS rules, as long as he is on the end of the line and isn't ineligible by number, he is eligible.

Yes, but an understatement as applied to 6s, where all players are eligible to receive a forward pass.