I am using a ED120 X 900 on the Bintel Skyview mount, seems to handle it no worries. There is the problem of vibration which does spoil the view at the eyepiece you need just a hand touch to steady it.
I guess this is issue when using that length tube on these style of mounts. is there a way to eliminate the vibration ? The Porta Mount 2 would also have the same issue with that tube? I know they are sturdier, but i don't think that is the problem here,the Bintel seems to hold it just fine, you can move it with one finger any direction no flexing.
Fill the bottom tripod sections with sand , put a seal of silicon rubber on top of it to stop it spilling out and reassemble .
This will add a lot to its stability.
Brian.
I had the ED100 on a Porta2 mount and it took a while to recover from shakes. I even tried vibration pads but the tripod just isnt solid enough. I would definitely not recommend it for a bigger scope like the ED120.
I now use a M2 mount on an EQ6 tripod and its very stable.
Fill the bottom tripod sections with sand , put a seal of silicon rubber on top of it to stop it spilling out and reassemble . 
