I wouldnt top them any more, i would just put the net up and start tryig to fill that up. Remember you need 2-3 weeks for the plant to fully recover from a topping. and 1 perhaps 2 weeks of veg to fill the screen.
Topping now would just cause the other branches to get bigger, if u wait a little longer then top the top two branches you will create 4+ main colas.
Purpose of topping it to create more main colas. If u use a screen this negates any topping because the screen basically creates a cola in every square.
I would not advise you to top. Put it this way, for every branch, tip, node or whatever you cut is thrown away. So what u do throw in the trash is just wasted energy i.e. Time electricity nutes ect.
my2¢