I made my seats and my girlfriend sewed them for me...I used a large piping to compliment the seat to hull. Always make things a tad larger as its easy to cut or sand later than buy more wood. My seat sits just below top side and the pipe finishes the difference and once seat is tightened down its about even. If the sides are in good condition without holes, you could have them underneath as in my kick panels...I just finished them an just need to add carpet.
