Hi DJWazza, Great to see someone taking the initiative and getting stuck in.
My worry though with these seals is when you do the hose test on them they might not be as good, or if they do manage to seal the A section you might find even more water ingress at the falling pillar seals, the reason being the Megane seals are not the usual EPDM that most manufacturers use, they are made from a harder type of rubber and much less forgiving than closed cell EPDM, therefore the positioning of them is super critical because too far out and they wont compress enough and will keep the door glass held further out than it needs to be to contact your other seals,too far in and you wont have enough pressure to make a waterproof contact.
I have a pair of these in the garage and there are always a few in the big yard, plentiful as you say, but personally i deemed them as little if any use on the Elan, far too hard for the Elan and a fair bit wider than needed, combined with windows that are not too rigid even at the best of times then it's always going to be tougher than it needs to be, even fitted to the Megane they have a bad reputation for leaks, from my knowledge of seals i would put that down to the rigidity of the material used in their construction.
Good luck though, if you can make them aesthetically better than the originals and pass the hose test you've done a better job with them than I could.
