RAM Mount - Which Suction Cup?

[k6uk]

RAM makes two different suction cups and very little information to help one decide on the appropriate choice.

First there is the large 4" one:

and there is the locking 3.5" one:

My 276c is coming and I'd like to find the best solution - anyone have ideas on which would be better for my application?

While searching for images to post, I stumbled upon someone using both a windshield suction cup, and a beanbag mount together:

I guess this could be a solution to the vibration problem - it's worth thinking about anyway.

 

[CAPTAIN COORS]

i just got the 3.5 inch locking, the thing really works well, once on anything smooth its hard to remove

 

[k6uk]

Thanks for the input.
I ordered the 4" one, and I'll see how it does.
If it doesn't seem solid I'll ebay it and switch to the locking one.

I'll post my results here!

-Mike