The forearms should be inline with the puttershaft. It is the same thing as going to impact fix with the right forearm in plane with the shaft (12-3-0) Section 2 Number 6. With putting the shaft will have better support with the putter and rear forearm in plane with the putter.
The reason for the left forearm in plane is a matter of sameness and a matter of alignment.
Gripping the Putter in the lifeline of the Left Hand -- not under the heel -- zeroes out the #3 Accumulator (Left Arm and Clubshaft Angle). Combined with a Level Left Wrist, this automatically creates a theoretical Left Shoulder Plane and an On Plane Left Forearm. This is the basis for the Pick Minor Basic Stroke (10-3-G) -- Elbows Bent and both Forearms On Plane -- described by Homer Kelley in prior editions of TGM as "Yip-free."
Impact video and analysis is from overhead and Ball level. Shaft Lean and Lie Angle are determined for your 'ideal' and compared to your current Putter. Address Clubface Alignment is checked by laser beam.
Call sales associate Cathy Tatum at 770-640-0933 to arrange an appointment. No charge for the fitting. Bring your own Putter.
Also, Henry-Griffitts pioneered custom fit Putter Systems in 1994. To schedule a fitting in Atlanta, call our own Ted Fort at 770-401-1086. For those elsewhere in the world, go to www.henry-griffitts.com/teaching.asp .