Marcin
Your beam is a great idea. This is something I've done on a couple of Soviet vehicles, and it can be a nice little touch of realism for the model. Good luck on that.
Just an fyi for you -- (for the Big and Beefy campaign), completion of the model, (in your case the SU), by June 1st, earns you a ribbon. If you place the SU in a dio after the campaign completion date, that is great, (and we'd love to see pics of that when you are done), --- but just so you know, if the SU is completed by June 1st, you have successfully completed the Big and Beefy campaign. Thanks for participating.
Steve