I have to use glass versa-tops, because I have cats and jumpy fish. My Finnex planted+ rest on top of the glass in all tanks.
They do produce annoying glare from the glass (mostly forward and backwards, towards and away from the observer), being blinding to me. I was very annoyed by this but solved in all my tanks by adding these cloth caps to reduce light escaping. I like the result very much. Good and simple enough. Don't have any idea about PAR of any other reductions and don't care too much as long as fish and plants are happy. They are.
The image shows 2 photos - Top, without the cloth cap, Bottom with the cloth cap. Glare solved and I prefer the look. In this 6 foot tank I use 2 3-foot Finnex.
Cap does not interfer with opening/closing versa-top, but I do need to pull them weekly while servicing filters (no big deal).
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