I see you already have an oil separator on the valve cover and a check valve at an angle on the pipe. Should work I think. The oil separator will keep any oil out of the exhaust so none gets on the slicks while the system at rpm should draw 5” of vacuum, at least according to the info attached from a boat performance site. Look towards the bottom of the page on the site for the info.
http://www.performanceboats.com/gn7-dyno/52702-header-evac-zoomies.htmlPutting a breather on the engine with a pan evac system would do no more than draw air through the engine and would create no vacuum. The vacuum is used to reduce power lost to windage and to reduce internal pressure due to cylinder pressure leakage past the rings.
You could disconnect the evac line from the oil separator and put a vacuum gauge in the line, fire up the engine in the pits, and see how much vacuum you can pull. The boat article said he was pulling 3” when he hit the throttle while still on the trailer.
Let us know how the system works out for you. As long as the oil separators are working properly, I would think it’s safe.