How are you using the H90? Are you connecting in mono or stereo? It matters greatly because algorithms are designed to behave differently in either case. For example, in mono, the Filter Pong delay algorithm works like one delay being fed into the other, just like you want. However, when connected in stereo, each separate delay is routed to its own output. Most Eventide delays direct one of each dual delay to its own output for a wider stereo image. Algorithms like Digital Delay, Mod Delay, and Vintage Delay already feature built-in modulation for width generation. How deep have you tried tweaking modulation capabilities on these effect types?
What delays have you explored? Are you sticking to just the factory Programs or have you experimented with the individual delay algorithms? In total, there are twelve. If you count algorithms like SpaceTime, PitchFuzz, and MicroPitch, which all have dual delays in them, there are even more.
Which modulation algorithms are you using for width enhancement?