They are under such low torque that a quality hardware store bought or Allen head with a spring washer should be OK, right?

Pretty sure the answer is yes but this seems like one of these things that’s worth double checking before it gets sealed up.

Thanks!

Was socket head stock? Most socket head screws are taller than a hex head bolt, you don't want to have problems with clearance

Excellent consideration. Thank you.

I believe these are M8x 15 hex head, Bruce wrote that you need to make sure to use grade 8.8 minimum.

I believe they are low tensile strength, high shear strength. Length is critical.

8x1.25x18 is what I found

Different than other references

Grade 10.9 from my local hardware store.. but they've got a fantastic fastener department. Fresh bolts, dab of locktite and you're good to go.