Punched cards - which paper/cardboard?

I have read the follow up e-mails too and wonder why you want to do this. If you want cards for storing data why do you need to print on the cards first? I have a loads (110,000) of cards of the right shape which I use for my mainframe. They are already printed up with every two columns marked out as one column of mark sense boxes but of course the mainframe doesn't see the markings. I have probably more than I will ever need in my lifetime. I even use them for keeping hand written notes and my ex-ICT engineer friend folds them in two, pushes the pins of a PCB through them and marks the bay number, carrier level and card position the card came from on them. If you want, I can sell you some at less than the commercial suppliers rate and I think less than they would cost to tool up to make them. Carriage is of course another question. I have been buying up local supplies of 11" by 14.5" fan fold paper for less than the carriage costs from say 50 miles away. I see your suffix is .de, I guess that's Denmark or is it Germany? At least there'd be no customs issues but I would think carriage would still be quite expensive. I'm not sure my card equipment would be happy without rounded corners. I know there were hardware modifications listed for dealing with cards with and without diagonally cut corners at leading/trailing edges. There's also the possibility of paper cuts for the operators. I think my IBM 029 keypunch uses the rounded corner to push the card guide down when it registers the card at the punching station. I think a square cut card would jam up.