Otherwise legal formation, five 50-79 and 7 on the line. Is it OK for #78 to not be covered? Obviously he isn't eligible but I'm thinking he can be there. AND hhy am I have a brain freeze on this???
Only place it's not legal is in the NFL. In the NFL, the player on the end of the line must be an eligible receiver.
That is the reason you will hear the referee announce before some plays that "#78 has reported as an eligible receiver". The signal is sliding his hands up and down in front of his torso. 99+% of the time this happens in the NFL, the offense has no intention of throwing the ball to #78, nor will he even go out for a pass. They simply want an extra blocker, but the last man on the line has to be eligible.
In FED (and NCAA), #78 can never be an eligible receiver, but there is also no rule requiring the end to be an eligible number.