Thanks. @pieper1973
I built the crossover board mainly for experiment to help my friend to upgrade his cs2.4. My 2.4 is the front L/R of all Thiel HT setup ( mcs1 center, powerplane side surround and two mcs1 back surround) so I didn't go too crazy and my parts selection is mainly depends on cost.
My idea is to build a xover board about the same size as the original factory board, so it can fit inside the speaker cabinet on the same position. I also add some nylon standoff on the board so it can seat up side down in a pvc project box fill with resin for vibration control. But I found that put the crossover outboard is the best way to eliminate cabinet internal pressure/vibration and fill with resin seems unnecessary.
About the capacitor choice, beside the cs2.4se, Jim Thiel design most of his crossover using bypass, including the cs3.7 and cs6. Therefore I also go with bypass.
However, my friend was using his cs2.4 for two channel music playback, he changed his mind to upgrade the crossover due to very high parts cost (he consider using Audyn's copper cap) and bought a pair of cs3.7 instead.