Oldschooldave - Yes, you can use caps on these and that is what I use. The capless harness is just to show you what they look like in a harness.
optical 2 - the feedblock will depend on the marker you are using this system on. The adapter I made for my Typhoon fits on the Qbow adapter.
Pizzaluvr - They are the same length as 10 round tubes and I guess I could do them from brass but they would be a bit higher in price.
Wading through a
mess, But I am moving forward...