Regarding this, the vertical alignment in question starts in a vertical curve with the VPI being 11 feet from the start.
In other words, while the vertical curve is 680' long, only 351 feet of it are actually part of the vertical alignment.
Any way to address these issues?
I believe the answer to your question is yes. VAL can start before HAL starts.
If your HAL starts at chainage 0+000 you can start defining your VAL at -1+000.