Hi
I'm still redesigning my new DIY fume extractor. The layout makes sense for a horizontal air pull. Is there any benefit, restriction etc for choosing between a horizontal and a vertical pull. A horizontal box would allow a straight run until piping up over the roof. The box would be cheap paper prefilters, a hepa filter, and about 20lbs of carbon. Also, I'm paying $260 for a rectangular 12x24x12 merv 17 hepa. I think this is larger than I need but was told a nonstandard size would be even more expensive. Can anyone recommend a hepa vendor? And do you think I'd be okay going with a smaller sized hepa? 12x24x12 seems overkill. Thank you!