Personally I avoid using a sliding float when targeting catchable rainbow trout in Lower Mainland lakes because it is unnecessary most of the time. Most spots are shallow enough that a fixed float with a depth set at 4 to 5ft is sufficient enough. Although the advantage of a sliding float is the ability to fish much deeper water, I find that you need to use bigger floats and weights so the weight is heavy enough to keep the line sliding down until the float hits the top stopper. The combination of big float, big weight and longer float depth means that the sensitivity is reduced. When the 250g trout bites, it'd be hard to notice. Because these fish are not very big, I prefer to use the smallest float possible while still having enough weight that allows me to get some distance when casting. If I wish to fish at the depth of 10, 20 or 30ft, I would simply use a bottom rig. Either a sliding weight above the hook or a fixed weight below the hook would work well.
Good luck.