because the straight pull bolt action SKS has been done already, you are not breaking any new ground here http://www.thefirearmblog.com/blog/2015/07/10/1moa-sks/
The mag thing has been looked at for at least the last 20 years, also nothing new you are trying to do there. Continue with your project, but if you want more then 5 rounds you will need to mod it for one of the AR15 pistol mags.
Saw a couple of other conversions but didn't like them for different reasons and simply offering my version for comment. With regards to the mag I'm not overly concerned if the powers at be decide that it remains 5 so be it and if they accept my explanation and allow me to restore the mag to its original 10 all the better.
Meanwhile I still need to do some sanding and polishing before my buddy welds it together .