Finder cutoff with 500cm too much hassel



I'm on the verge of purchasing a 500 series but I'm at a crossroads. I have concerns about the finder cutoff that seems to be a problem when using long lenses and the 500cm. I plan on purchasing some tubes and a 250mm.

What are your experiences when using long lenses with the 500cm? Is the finder cutoff something you get used too? Or should I save my pennies for the 501cm?