Honestly at the 280-300' range staying in that speed 7ish range maximum is best if you want a dead straight flight. Discs like the Saint and Escape do have a ton of glide, but they are still faster discs and will fade at <300' shots. Like a mellow Thunderbird as others have said. The Saint does beat in, and I feel like it needs 330'+ to be a laser straight glidey disc, and I think it shines when you can throw it that far without trying full strength so it becomes a glidey tunnel shot disc. So basically I think it would fly -0.5/2 at 300' or less instead of an easy glidey dead straight disc. Still a good glidey control driver for that type of throw, but definitely not the dead straight tunnel glide disc it is at higher arm speed.
The Discmania FD is still my pick for something like a Leo flight, with a little more speed, and extremely neutral. If you want to go up in speed then the Sidewinder is good, but just because it is understable enough that it won't fade out too much at that range, and it definitely goes farther than the Leo by a full disc class.
I don't really have any Trilogy recommendations in this position, I really think the speed 7 range is where they need to get some more discs. There are lots of their discs I haven't tried though. I have no way of knowing how beat in or stable your DX Leo3 is, so things like an Underworld could even work if it's on the heavier and more stable end. The Renegade, which I have thrown one of, made me think of a Sidewinder style of flight and range. The River definitely fits this criteria, it has very good glide but less consistency than the FD. It is not power hungry either.
