Currently considering some chassis rails for my mk1. It’s between the reinforced Jass Performance or Skidnation with the potential for a butterfly brace upgrade in the future.
Hi @Mk1Jack i’ve not fitted either of these as concerned with trapping filth from the road between the chassis rail and original structure as time goes on… bolting into or through structues in the underside i coudln’t see as a long term solution… i hear they improve rigidity though so as in all things it’s a compromise?
Hi @Blue_Ben, that’s true and something I’ve considered myself. I think the relatively short-term preservation of my current chassis rails seems better than leaving them. Of course they could be cut out and replaced with thicker 3mm sections but that would only be an option if my current rails were completely ruined. I’ve yet to decide but it appears like a good compromise of increased rigidity but with the added maintenance of keeping them clean.
@Mk1Jack Agreed Jack. As they can be kept clean… with a bit of TLC 
Our Mk1 suffers more chassis scuttle than the mk2.5 owned before, i think Mazda beefed up the under body braces much better in the MK2. Then there’s other mods like three point engine brace, chassis bolted roll bars and enhancing the braces across the chassis that i’d love to do… am sure the enhanced rails will do a good job!
I’ve had the P5 frame rails for over 10 years on my NA, with no issues regarding corrosion or needing to clean them. Together with a 3 point engine bay brace they make a big difference to rigidity. Highly recommended, I doubt there’s much difference between the Skid Nation and Jass offerings - they’re all based on the original Flyin’Miata ones.