Van’s have a (cheap!) perspex and metalwork kit available to modify your wingtips, and we are in the process of making some boards to suit this kit.
The only problem is, Van’s have almost run out of stock and intend to obsolete the parts. Please send us a message to say you’re interested in the kit, so that we can get an idea of numbers and hopefully convince them otherwise, or alternatively we’ll second source the components.
edit: The wingtip modifications required are detailed in this document: RV4&6 WING TIP LENS KIT