[50mhz] Stacking interaction with 15 & 20 monobanders?

[N3XX - Tim Heger]

Looking for opinions on possible interaction if I mount a 6 Mtr yagi between my existing 15 and 20 Mtr 5 element monoband yagis on the same mast.  The 15 and 20 Mtr yagis are 11 ft. apart on the mast, and I would be mounting the 6 Mtr yagi midway between them.  So about 5.5 ft. distance to either of the yagis above and below.  The 6 Mtr yagi would be 5 elements, on an 18 ft. boom.  Would like another element or two, but don't want to add too much more wind load to the mast with the additional boom length.
I'm afraid the other antennas would be too close, and possibly the 6 Mtr yagi wouldn't perform well in this configuration, but trying to save on the additional money that would be spent to rotate the antenna with a side mount arrangement on the tower.
I guess I could just go ahead and put it up there and see what happens.  It could always be moved if there is a problem.
Or, maybe someone has a good low cost solution to antenna rotation with a side mount.  The TIC rings are nice, but would be spending about 3 or 4 times more for the rotator than was spent for the antenna.

Thanks - 73,
Tim - N3XX