Optec

When you have a normal eyepiece from an regular manufacturer - and when you use our T-2 eyepiece clamp - this cannot happen.

The small Synta refractors don´t have the necessary backfocus and tube diameter for attaching the Diamond Steeltrack, therefore we have no adaptors created for this size

The parts you mention should work fine to connect the UFC between the diagonal body and the 2" barrel. However, due to the threads, the end position of the UFC cannot be adjusted to your preferation, it might stop at an unfavourable position. We are thinking about developing an Camera-sided UFC adapter with S58 dovetail receptor. This would allow exact positioning to your needs. However it will take months before this product may come to the market.

Its hard to answer this question in general. Yes, the MaxBright II Binoviewer will work with an Celestron 11" EdgeHD. But there are many ways to adapt it. Most (if not all) customers will use a Binoviewer on a SC telescope in combination with a star diagonal. There are many different star diagonals available (or even our Baader FlipMirror II) and many possible ways to adapt it. We recommend that you look at our extensive 24-page manual, which illustrates many possible adaptation options and required adapters: https://www.baader-planetarium.com/en/downloads/dl/file/id/1614/product/4317/manual_baader_maxbrightr_ii_binoviewer.pdf

Furthermore we recommend to take a look at our PDF: Manual and Recommended Use of Baader Star Diagonals (T-2 and 2"):
https://www.baader-planetarium.com/en/downloads/dl/file/id/1617/product/1687/baader_star_diagonals_t_2_and_2.pdf

Unfortunately we don't sell the SolarMax III and don't know its thread sizes and most of all the available backfocus (but we strongly assume that it is very much too small). So we cant comment here on required accessories or functionality.