With -7.5dB Preamp gain, Balanced output,
you will have no clipping even at the max. 4VRMS output level.https://drive.google.com/open?id=1gYu-UCC19OOLxBjvS5zSRXTwpD29h9cem1431qlKnJo
Ideally, with -7.5dB sine wave, you will get 113dB SPL - 7.5dB = 105.5dB SPL.
Please check the figure #2 in page below:https://www.shure.com/en-GB/support/find-an-answer/understanding-earphone-headphone-specifications
By the way, what do you mean by "-7.5 dB for my PEQ settings"?
-7.5dB preamp gain?
The real audio signal doesn't have all energy at a specific frequency band.
For 31.5Hz tone, boosting EQ up to 6dB at 31.5Hz may require -6dB preamp gain to prevent digital domain clipping. However, the real audio signal doesn't have its all energy at 31.5Hz, so you don't need to have the same amount of -6dB preamp gain, in most cases.
Boosting EQ up at a specific frequency band and setting the preamp gain down is to keep the signal swing at the same level. Eventually, the overall SPL would remain at the same, if adjusted properly.