Cleaning the exposed part of the sail with in-mast furling

Much simpler to have a strip of top grade UV resistant Sunbrella stitched to the clew. Colour to match any other canvas work on the boat. May still need the odd clean just like any other canvas but looks infinitely better than slightly grubby white sailcloth.
 
Would a weak solution of Patio Magic do the same thing? I bought some to do lines, ropes etc that cant easily be removed and put in the washing machine. If so any suggestions as to what ratio of PM to water.
 
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