Roy,
Thanks for the pertinent points raised in your post.
I might add that since the element centers are close to the mast
I have avoided the installation of a boom at the top of the mast
as one would do to lower the take off angle by the use of a stacked
beam. This 'top beam' provides major instability when using a single
mast. With me using my normal fishing pole elements the arrangement
will help quite a bit in mast mechanical terms. Since it is element
height over the feed element that, in the main, is creating a
compressed lobe (as I believe your post infers) I will take a different
tac with respect to the driven element, where it will be the only
element shaped in parabolic form and all others will
remain in a "V" configuration( straight portion for clamping at the
center). The parabolic shaped driver would then hopefully allow the
addition of staggered elements for other bands. The mast used will be
a 2 inch diameter fibre glass to prevent vertical radiation mutations.
Regards
Art