If you use WA lenses, make sure that your bellows assembly contracts short enough to attain focus at all column settings. I cannot for instance use a 40 mm lens for 35 mm on my Durst M605. Although I have no idea, it may be possible that some 4x5 enlargers do not allow for such short lenses to be used, unless they were designed for all image sizes down to 35 mm, or at least one or two formats down.
Durst do recessed lens boards, the two I have to hand, one measures 15mm deep, the other, 35mm deep. The downside with recessed boards is being able to adjust the aperture and/or see the scale.