unlucky weasel, I would scrap the bubble and try trotting a bait through the run with either a stick or trotting float.
Using a bubble will put a lot of surface tension on your hook line, meaning the trout will feel the float as it tries to take the bait.
Fish the stick float to the desired depth with a team of split shots above your hook.
Minnows are deadly for trout, slowly spinned through a pool.
Also I'd use a size 8 for big trout