Some good points!
In fact, the Lowes associate suggested that the 30 degree Hitachi gun might be better than the 21 degree one. But it shoots clipped head and I preferred full round head.
We'll see how things fit when I take the gun up there.
Tail extension is only going to be enough to get a continuous vent installed in a soffit. It is also because the ends of the existing rafters have deteriorated. Putting new fascia boards on too. Will use 2x4's that extend up the rafter a ways, so should have lots of room to work. Will probably replace the first 1x board on the roof, so access outside should be good too.
How forgiving of size and make is the Hitachi NR 90AE (S1)?
Bill
Ah, I see now. Yeah you should have no problem pinning those with your nailer. Two things;
1. You probably know this already, but soffit vents are useless unless there is a gable or ridge vent. Also, I've seen many a soffit vent rendered useless after the insulation was done and packed into the eve at the roof deck / wall top plate area cutting off the air flow.
2. String line your rafter tails (regardless of how good existing is) and use the best lumber for your fascia. It will make life so much easier for you during installation and for later applications (like gutters) esp. if capping with aluminum. Not only that but the house will look nice and straight regardless of existing framing and there will be a nice straight line to nail on your drip edge.
As far as your nailer goes I can't really help you there. I run a Bostitch. But yours is a 21 degree which is an industry standard. You should have no problems finding the right nails in your favorite flavor. Mine is also 21 degree full round head and have had no problems with any of the nails in the big box stores. Someone had already mentioned Maze nails, you can pretty much get anything you want there.