as a notoriously lazy builder I do like flying wings and have designed and built quite a few.
I noticed your tip fins were tall and thin and would recommend you make them longer so the high pressure air from the underside of the wing doesn`t rush over the tip to the top of the wing and ruin the low pressure air.
Ideally you want a little bit below the wing and a higher portion on the upper side.
It`s not a criticism, but I think you have stuck your fins on the wrong way, if you need to , just relieve some of the elevon to stop it rubbing.
This ain`t one of my designs it`s just for example
Always open to suggestions. i just built it to the plans I was given. I really like the idea of a shorter fins and it also makes perfect sense to have some below the wing. I will definitely give it a try.
Take offs are optional, landings are not.