Mounting an ARRI ALEXA 35 with Zeiss Super Speed lenses on Steadicam® with minimal height: mattebox options and rod support alternatives.

2023From a Facebook group: The Steadicam Group

DisputedParticipants disagreed and reached no conclusion. Read the findings as positions, not as an answer.

The clipping pressure of a clip-on mattebox can make the focus ring of Super Speed lenses stiff; ARRI solutions for 15-mm lightweight rods (BPA-6, CBP-5/6) are bulky and tall, and CBP requires an additional dovetail plate.
A 15-mm rod support mounted from above using an LMB 4x5 with a 143-mm clamp adapter works on all LMBs; an R2 ring from the MB-19 with a reducer from 114 to 80 mm keeps the rod support optically centered equally whether mounted above or below.
The lower half of the BPA-6 is removable and saves height; an LMS-4 top plate mounted under the camera paired with UAP-3 plus LWS-6 yields the flattest base plate with centered rods, though this loses the rear attachment point.
Third-party solutions include the Octamas ALEXA 35 Bottom Plate with integrated 15-mm lightweight rods and ARRI dovetail clamp (approximately 262 g), described as the lightest and flattest option; Catgriller dovetail fits directly into the top stage with 15-mm rods front and rear (19-mm adapter available); Wooden Camera ARCA plate and cam-jam rail plate kit are further alternatives.
Some operators report that most MKIII Super Speed lenses tolerate a clip-on mattebox if focus is calibrated first and the clamp is tightened to only about 75 percent.
Minimal solution: threaded filters or an 80-mm Series-9 filter holder with rubber lens shade.

Whether clip-on matteboxes actually impede focus on Super Speed lenses is contested among operators.
Solutions depend on the specific Super Speed lens generation and focus calibration.
Height savings versus functional features (rear attachment, stability) involve trade-offs.