Redoing a teak forward hatch that, unlike a lot of the woodworking on my boat, is not of the best joinery work. It is constructed as a wood frame with a plexiglass top. The corners were mitered, but gaps exist that detract from the appearance of the hatch. What would be best to fill these gaps with considering that I need something durable and something that will look good when varnished? Remember, this hatch will be opened and closed a lot so I would think the frame would be subject to a lot of twisting. Silicone or polysulfide would allow for the flexibility but would look lousy when varnished, while a putty type wood filler is almost certainly to crack and fall out. One possibility I am considering is trying to color epoxy with teak saw dust in an attempt to make those filled spots blend in better.