advised against wedi?! by who? for what reason?! that's like being in the market for a new 4x4 and being advised against a landrover in favour of a ford fiesta! 😀
By competent plumber who installed both Wedi and OTL and preferred OTL for being more rigid and well supported waist design.
I wonder if someone who has installed OTL could reply to say if they just used tanking that comes with the kit or used any extra for waterproofing. Their German tanking staff supposed to be really good and not needed extra membrane.