The stereo windshield AG kit is correct basket solution for the MKH 30/MKH 60 M/S pair. Our general rule of thumb for calculating the correct basket length is microphone + 50mm (XLR length) for the body length.
However in the case of the stereo basket, the additional diameter allows the cable more more than the smaller mono baskets - so the 280mm of the MKH 60 will fit inside the AG perfectly. We would also recommend the addition of the optional Connbox CB3, all details below:
Description: Stereo Windshield WS AG MS Kit
Order Code: 080201
Web link: http://www.rycote.com/products/080201
Description: Connbox CB3 (2XLR-3F)
Order Code: 016924
Web link: http://www.rycote.com/products/016924