Unfortunately we have no means in countering any obstructions on a supporting wall, the Wall plate we provide only comes in the one format which needs a completely flat surface to operate upon. the water in the verandas will normally go down the internal pipes hidden in the columns, it may be possible to adapt these further but we cannot again advise how.
Please also note, As we do not know what you will be fixing the main wall plate to no fixings are provided with in the kit. Most will purchase specialist Fischer expanding screws for the job however it does depend on the wall in question.
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