Yes there should be a seal at the bottom of the screen to the scuttle. It has a short "T" top that slides into the channel on the underside of the lower frame and something like a 1.5 inch tongue that sits on the body. I think you may find that the channel may be a bit worn away in places....I seem to remember at the ends where rub on body brackets...so that there is not enough channel to hold the rubber in place at those points. There may be a possibility of building up with brazing and recutting the channel?...check before you get the chroming done. The rubber I bought many years ago did not fit particularly well but stayed put for many years......you have just reminded me.....I should have had a go at mine before I had it chromed.....now it awaits reassembly.....probably have to use glue at the ends 
Dennis
Dennis