If it really is 1/4 gap that is questionable install. When the customer wants a floating panel, with get slope on the curb and a 1/8max gap and the water stays in the shower. They do make plastic sweeps for glass doors. You may be able to get one of those to work. They get nasty also, but you toss the and get a new one. Caulking is a bit of an art. I don't let anyone do it on my job except me and the painters.