@shootemallagain
As long as the structure can support your weight, and the force you exert on it, than it will work.
As far as the rope length is concerned, that will depend on your method. Based on the knot you have, that looks to be the hangman's noose. While that will work for any method, it is best suited for the drop hang, which may be best if you use a higher tie-off point.
I've included a few links to to the major hanging resources this forum has. I reccomend you read them thoroughly.
https://sanctioned-suicide.net/threads/how-to-hang-yourself.1183
Knots in Alphabetical Order. There are 196 knots listed (animated) and 374 total knots as some knots are known by several names. Select by Activity, Type or Search for Knots.
www.animatedknots.com