Silencers and chronos aren't a problem, silencers don't knock power down unless the pellet clips. You will be taking the reading from the length of the silencer away from muzzle rather than actual MV and as we all know the pellet should be slowing as soon as it leaves the muzzle but this amount isn't significant. It'll be less than 1% over the first yard so nowt to worry 'bout over a few inches.
Skan chronos come with a warning that some silencers can have effects on the recorded velocity but also they tell you to keep the muzzle at least 10" (254mm) from the chrono to stop air blast affecting the chrono, it could vibrate the sensors and cause inaccurate results. They claim some silencers concentrate the air blast but this I think applies far more to "air strippers" which can actually increase MV by a few FPS depending on design and how they're set up. I wouldn't recommend attempting to try to use a Combro on a gun with a stripper attached.