Did I make a mistake on my seat. illegal or not

[Rob Petrie E395]

I took my drivers seat apart and put a plastic tube through the bottom of the seat so that the "crotch" strap can go through it up from its mounting point to the cam lock. I figured this would be better than running around the front of the seat and then into the cam lock. I did not remove anything from the seat what so ever. I simply slit the cushon made a rectangular tube out of a piece of thin plastic pipe. Then I took it to my local upholstery shop to have it sewn in and finshed so it looked nice and professional. My thought was that if something ever happend it would hold me back in the seat instead of letting me slide down and forward before the "crotch" strap was able to do its job. Then the other day I was reading another thread that got off track and it was mentioned that this may in fact be illegal but noone ever commented on it again just that one post. If I screwed up and ruined a seat bottom let me know. I would rather throw it away than have something thats not right. My main goal it to make to the track with this one. my second is to be completly legal and third run the index or better. If I can do all that and I enjoy the travelling I will continue to try and get faster legally. I just dont want to show up at my first race with it and be told that its a bunch of illegal junk. Thank you for your opinions