I am planning on using some aluminum angle to mount my oil cooler close to the engine on the stringer. This will not have to support a lot of weight and will have 4 brackets, so would you suggest just screwing it to the stringer or using a through bolt? Also do you use something to seal the exposed wood after it has been drilled?
thanks

Through bolt.
Sealed mine up with 4200

I just did exactly what you're talking about.

I used 6061 angle and through bolted with a stringer washer on the opposite end. I actually painted inside the drilled holes with a hobby brush and then sealed all the holes with the 3m 4200.

I had all my aluminum brackets annodized so they wouldn't corrode and they look nice too.

Wow that looks so nice vintage chromoly. Thanks for the info guys, will get the holes drilled and sealed.

Black zip ties would look better

Good eye Griff.
Rest assured, those are cheap ties and only for mock up.
The permanent Ty raps have the metal tangs in them and are black.