Surfside TM-14 Door Gasket Advice Needed

[Happy Vongole]

I am looking to replace the gasket around my surfside door. I am pretty sure that I will not be able to find an exact replacement so have been working with some local RV stores here to look into replacements. I was given the suggestion to use a door gasket that is a U-channel type (clip on with side bulb). The site is 1 inch width x 5/8 inch thickness. The flank size is 1/8 inch.

When I put the sample on my door it did not seem to fill the door channel as the original did. It seemed quite small. The RV specialist I was talking with thought that this was okay.

I am looking for some advice about this. Does the gasket need to fill the entire door channel or is a smaller size okay. I have attached a few pictures to help clarify what I am asking about. Thanks!

[Old Macdonalds]

I am renovating our surfside and another poster recommended swiping a gasket off a minivan door at the wreckers. Went and got one. It is more than long enough and they let me have it for nothing. Haven't tried it yet but am hopeful. The price was right anyway!!

[Happy Vongole]

I did see posts recommending that as well. I have not been to the wreckers before so perhaps it is worth a trip!

I guess I was also wanting some advice regarding the coverage needed for the gasket. Does it need to fill the entire door channel?