Find the studs inside the gable - hit them with your fasteners.
The "rule of thumb" for fastening through Vinyl siding is - pre-drill the
siding - 3 to 4 times the thickness of the fastener.
We would caulk the holes with some type of urethane/poly-urethane
caulk - "Quad", "Solar-Seal", etc...
Tighten the fasteners "snug"; but, not "dead tight" - expansion.
Probably, use galvanized screws.
Vinyl siding expands and contracts quite a lot.
You should pre-drill it.
The siding itself, will support VERY little.
If the siding "oil-cans", buckles, distorts ... because it's "locked" in place -
even if you remove what's preventing it from expanding/contracting -
the damage is done - time to replace it.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!