Hi Mickey
The only problem that with the rain channel was that the top channel is lower than the side frame. My solution was to space the side plates away from the main frame gradually to about 5mm, fill the gap with bonding filler and run a grinder down so that the groove sits slightly lower than the top channel. it goes down the side for about 30cm. Not sure if others have found a different solutions but I've run a hose pipe on it and it drains fine.