RE: Dle 20cc and seagull extra 260 .90?
The DLE20 will fly that model fine, but be lacking for pull-out from a hover.
When hovering, you should be at 50% or less throttle, so that when you go to pull-out at full throttle it'll do so promptly, not sluggishly.
I have (2) DLE20's, one on a profile that's 7 lbs and pull-out is like a rocket!
On the other at 8 lbs, it'll hover, pull-out is slower but acceptable.
The model you're wanting is heavier yet, and could hover, but struggle on pull-out's.
For that model, a DLE30 might be better.