should I compensate by adding to the 5 exposure
Yes, you can and you probably should compensate for the shorter exposure, but bear in mind that this will change the final contrast you perceive.
Longer grade 5 exposure can lead to too-black blacks.
That depends on if everything is flat, or mainly highlights or shadows.
Also, keep in mind that grades 4 and up require more exposure than middle/low grades to achieve same densities.
You can do a test strip for different low/high contrast exposure times. They do not have to be 50% each. In fact, I see no point to it. I saw no difference between 50%/50%, and single grade printing, though I'd have to try again to give a more precise answer, as it's been almost two years now I don't do it.
If you don't want to dodge or burn, you can try to increase low contrast grade (0.5, 1, even 1.5), to increase highlight contrast, if that doesn't make any of your lights full white. If so, go back to grade 0 or 00.
You can also change the total exposure time. Remember.
Some test strips will help. I know no shorter way.
Maybe If you upload some images we can see, we could be more helpful.