But how can you be sure the problem is not in specific element implementation? DBMonster tests show that performance in rendering is ok. FWIW - I develop on fir

But how can you be sure the problem is not in specific element implementation? DBMonster tests show that performance in rendering is ok. FWIW - I develop on firefox with shady DOM and then test in full shadow DOM in chromium - performance was very good for us in both firefox and IE (at least for the things we used).