How can i cull the lines outside of the surface boundary

i followed a tutorial on how to do a lunchbox truss system script on youtube and want to limit the curves to boundary of the surface i understand the the surface is irregular but im not good enough with grasshopper to understand how to fix it.

weird srf.3dm (68.8 KB) (8.9 KB)

ive left an image and the files it that helps

This could be a workaround but, you may get some overhangs along with your surface boundary edges. (28.9 KB)