Hi Quill,

I have had my most success using laraval imitations, fished mostly bouncing on the bottom. Here in the East, I have a "local" pattern which I have caught trout on in every state I have fished in, at all times of the year. It is called the Sand Caddis and is very simple:

Hook: #12 to #16 Mustad 3xl or 37160 (curved shank, #16 to 20)
Body: Ginger Australian Possum (various shades have all worked for me)
Ribbing: Gold fine wire
Legs (optional): lemon woodduck or substitute, tied beard style
Head: dark brown mink with lots of guard hairs

You can tie them weighted or unweighted. It is possible that the trout take it for a cased caddis, in addition to the tan caddis species which hatch here throughout most of May and into June...
Good Luck!