I wouldn't worry about reasonable rise being so close to the exam... just try to put in your best foot forward. You can score +/-15 points from your NBME just based on your mood and mindset going into the exam....if your goal is 235... I believe it's very doable. if it's 260, I would also believe it's highliy unlikely (not impossible... just not realistic)
How many NBME's have you taken? does it consistently show a weak area that you need to work on... if so, i would say work on those on specific areas as well as go through F/A once more...
Only you know where you stand... just determine where you are, with all your study plan as a whole and check whether it matches with how you've been performing thus far in the qbanks...