No, try Lake Dennison a couple miles up the road. ReseveAmerica will let you know what sites you'll fit on. All Mass State Parks have to reserved online too.
I have not seen a 45-foot trailer on the otter River side but I have seen them on the lake Dennison side about a mile-and-a-half up the road, otter River State Forest does have a couple of group sights big enough to accommodate a trailer that size, .
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