We use the Hunter Douglas Sovereign system which is renowned for its strong aluminium slat. Available in 16mm, 25mm, 35mm, and 50mm in a variety of colours and finishes.
The slat is approx one-fifth of a millimetre thick- which makes it twice as thick as some slat! All the components in the headrail are immensely strong; the system is also marketed under the ‘Luxaflex’ name (ours are cheaper of course!) So our Venetian blinds are probably the strongest available anywhere!