The data for M51 came out of gear testing but once the data was acquired I decided to try and put together an image.  The first data set was testing the Takahashi 85 FSQ (focal length 450 with no flattener) using the QHY 600M and RGB imaging. This yielded a huge field of view with a very small rendition of M51 in the center.  Coma at the edges as expected.  The next test came a few days later with the  Astro-Physics GTX 130.  No flattener was used.  A trial of the BARADV.  I didn't have the  correct backspacing so the corrected magnification was a little bit more the the optimal 2x.  It came out at approximately 2.2x for a focal length of approximately 1914mm on the AP GTX 130. Same target M51 but this time using lum filter.  The images looked pretty good so I decided to attempt to combine the RGB Takahashi images on the QHY 600M  with the lum images obtained with the AP GTX 130 using the BARADV and the QHY 268M.  I had low expectations that the widely different data sets could be combined but why not give it a try.  The key to the process was to process the RGB and lum data separately.  Then to crop the RGB combined image to match the approximate size of the lum image.  Once the processed images were close in size, a star alignment was performed and the RGB and lum images could be further processed  and combined as normal.  To my amazement, the final image looks pretty good considering how different the initial lum and RGB images actually were. 

As an aside, I followed Sarah Mathews two part tutorial on Astrophotography Galaxy Processing Workflow which was a great help in tightening up my own workflow in pixinsight. A few twists were added to my current processes.  Generalized hyperbolic stretch for advancing linear data into the non-linear state is my new best go to tool and the many tutorials on this subject are definitely worthwhile.   GHS is a must for everyone to learn.  Special thanks to Bill Blanshan' s star reduction tools and Russell Croman's star exterminator and blurX tools