300mm . . . what camera/lens is that? Nadir shots pointing straight down rarely make sense - but in the AllViewÂ´s case you can shoot aside the base by turning the vertical arm, so it might work.
The question is: what focal-length do you use? You know that a L-bracket provides more options to adjust the camera/lens fore- and backward? P.S.: Josef (Panoneed) makes an extremely versatile L-bracket. IÂ´ll drop you his mail-adress.
Yes please do send me Joseph's email address. I don't need a full L bracket, just a rail that is long enough for use with the AllView L bracket.
I have six different lenses for my Canon EOS 500D, but my favorite because of the quality of the images is an EF-S f2.8 17mm-55mm.
The extension rail to 330 mm will permit nodal offset for all my lenses including the EF-S 18mm to 200mm telephoto. I use portrait mode mounting.
The standard rails are max. 180 mm and will not allow nodal adjustment for the bigger lenses.
About the vertical extension pieces - I don't want to risk the camera + lens ever hitting the base of the mount if the software config is wrong.