I have both those fish in my 130D with absolutely no problems, they actually get on well and swim together.
If you are adding one to the tank having already got the other angel established, then i recommend you move the rocks around as you add him and also make sure the new addition is the same size or slightly bigger than the established one. This is what i did and it worked for me.
I have a flame and a lemonpeel together and they get along ok. However the lemonpeel has started nipping at my corals its always a chance we take keeping pygmy angels in our reefs but imo worth the try.
In a 250 it is worth trying but like others have already said it might not work out. I love lemon peels and flames but have not had the courage to try both at the same time. My tank is not as big an yours however.