Ah, I forgot about chromatic aberration. 
Too much time spent with reflectors. That said, my Dilworth despite being similar to a classical Cassegrain though with spherical mirrors, has a series of achromatic transfer lenses. I have never noticed any chromatic aberration when imaging.
Again, the best way is to suck it and see. If the unfiltered images are not too bloated (and they may well not appear larger at all), set the photometry aperture perhaps just a little bit larger to compensate and measure the same field with the same exposure on the same night (i.e. consecutive images) filtered and unfiltered so that the sky conditions are as similar as possible. Use the version which gives you the better SNR.
As always: SNR and cadence is what is important; aesthetics doesn’t get a look in.