Yep, I replaced the float alpha (for FsX) with a blank white alpha. Also for FsX I considerably darkened the prop alpha.
Thank you Roger, that fixed it. Is there a short explanation as to how this worked?
For the floats that have reflective material, the white alpha channel makes the texture less reflective and so reduces the overall shininess. The prop which has trasparent material is enhanced by the darkened alpha channel to make it more transparent which in FsX reduces the effect of "prop behind the clouds", common in ported-over models.