Hey there GOofy- I don't know for sure but it is a palmers and the feednecks are 7/8 o.d. and I have made many of those.
The total length of the standard feeders are 6 3/4" long and hold 11-12 rounds.
At a 5* the stand-off would be about 1 to 1 1/2" to top of feeder.
Any angle is fine and will work well. The more angle = the more positive the feed.
Hope this helps...