ah rubbermaid tubs... what would we do without them?!?!?!?
i dont see any problem with your set up, but...
watch your float valve, if the area around the valve has low/stagnant water flow, in the past i have found you will see kalk precipatate begin to form around the valve, which may prevent it from working properly...
a fix i use, is to put a small powerhead, (like the little free ones from the IO salt buckets) directly underneath the valve, this will allow the water kalk water to mix with the sump water as it is dripped in and will the valve from getting clogged by the kalk precipitation.
before adding the little powerhead, i would just run my fingers over the valve every week or so to dislodge any precipitation that had formed on it.
HTH.