I did the skybolts for the entire cowl. I think you could complete the firewall portion before the engine.
Make absolutely SURE that you don't have any interference with the skybolts at the engine mount corners. If you get them too close to the mounts, you will have interference.
That being said, I really like the skybolts and would do it again...
Aerospace Engineer '88
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Dues Paid 2017,...Thanks DR+