You are definitely better off having it modded because of the increased red sensitivity and Ha is well inside the normal filter cutoff point. But having said that you will still only have 1 in 4 pixels recording the Ha. The baayer matrix isn't removed so the groups of 4 pixels that read RGGB will still only read RGGB so it will never give you the resolution a pure mono chip will.
I like to use a UV/IR filter on mine. Whether its my imagination or not I don't know, but I believe that using one helps to keep the stars tighter by preventing IR from saturating pixels too quickly.
btw mine only has a glass cover replacement over the chip, i use the filter attached to my Focal Reducer or have them protecting the front of my widefield lenses. I see real value on adding them as the replacement for the existing filter unless you want to do IR imaging which a number of people here have done.
Paul, have you ever experienced the 'checkerboard' problem as descibed here?
I was going to replace the filter on mine with glass, but after reading that site decided to err on the side of caution and go for the Baader.
I've just checked and I was mistaken. My camera has the UV/IR filter already installed. So I guess I'll have a redundant 2" UV/IR filter up for sale soon.