I've had simular happen to me lately, it's reasuring this happening in a way
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I'd fix it to the inside of the lexan top myself, that way it's not obscuring any vital Cu surface area!, you could fashion a couple bits of plexiglass to shape then glue them to the lexan, use a glue you can get off till you're happy with the results. Or fill the channels with silicone sealant, let it cure then pull it out, then cut it to shape, stick it back to the lexan with more sealant. at least it's reversable and does'nt mark the lexan...
What do you think about some heavy duty turbulators?, copper coils like Dodge Viper?. we can afford to make them quite restrictive as we want, I'd like to widen the outer channel as well, make it a higher flowing block, restrictive is only good if used wisely...