Should Bare Metal Be Protected After Enlarging Holes for Curt Hitch Installation

Updated 08/10/2026 | Published 06/17/2026

Question:

I ordered the C22MJ for my 26 crosstrek. It looks like Ill have to widen some frame holes but no mention of sealing any of the bare metal that I expose from removing material. Is that not a concern in this area or should I paint it or something?

asked by: Steve E

Expert Reply:

Hey Steve! I do recommend coating any exposed metal after enlarging the access holes. The instructions for the # C22MJ don't specifically call for it, but a little spray paint, primer, or undercoating on the bare edges is a good idea to help prevent corrosion down the road.

The hole enlargement itself is a normal part of the installation, and is necessary to fishwire the mounting hardware into the frame. Once the exposed metal is protected, you can continue with the installation as outlined in the instructions.

What are you using the hitch for?

expert reply by: Robin H

Curt Installation Instructions
(click to enlarge)

Steve E.

6/19/2026

Ok it came in yesterday and I did end up putting undercoating on the edges I trimmed. It will almost exclusively be used for transporting bikes. The beefier one was probably overkill but ebikes a super heavy and im paranoid. I dont ever imagine actually towing anything

Robin H.

6/19/2026

@SteveE the Class III is a good choice, and I almost always recommend it over a Class I or II hitch. The 2" receiver gives you more options for bike racks, and more capacity never hurts. Sounds like you are all set since you applied that before installation. If you need anything else don't hesitate to reach out!

Will V.

8/10/2026

I've installed an eTrailer hitch on my previous Impreza, and it went well and did not involve drilling the frame. We've already added an expensive rustproofing-undercoating treatment to our new Impreza Hybrid, so hacking into the frame worries me; rust is a terrible problem here. Why does the other hitch available (much higher priced) NOT require enlarging the holes? Do these photos show that a grinder bit was used to make the existing holes somewhat slotted--as opposed to drilling out larger? Are they all (four?) ground this way or just two? Your description says MAY require enlarging the holes--only on Tuesdays and Thursdays, maybe? Why do comments suggest using a step-drill, which would make a larger round hole versus the slots? Thanks, Will

Robin H.

8/10/2026

@WillV I definitely understand the concern, especially after you've already had the rustproofing treatment done. The reason we say the holes “may” need to be enlarged is because there can be some variation in the factory frame openings. If the hardware will pass through as-is, there is no reason to remove any additional material. If you need more clearance, there isn't a required shape or specific method for enlarging the opening. The photos show the existing hole notched out enough for the hardware to pass through, but you could also use a step bit to enlarge the entire hole. You're really just removing the minimum amount of material necessary to get the hardware into the frame. Unfortunately, days of the week have nothing to do with it.