Quentin, I have a fly which behaves just like you are describing.
It wasn't deliberate on my part, just turned out that way. It sinks slowly, nose down.
Its basically a Hi-Tie pattern made with bozo hair with stick on eyes. The sink effect comes from the two globs of epoxy I applied to keep the eyes in place. You could experiment with different amounts of epoxy and its location on or below the hookshank. And of course you can use pantone pens to get some very realistic perch coloring.
When sight fishing, look over your shoulder from time to time, you never know who's behind you