Without card guides, the cards in my reproduction SCELBI are not as stable as they should be. They will rock back and forth a bit, even if just gently touched.

I just received a set of card guides for my reproduction SCELBI 8H. I installed the first pair on the front panel slot and they fit fine and hold the card in a very stable fashion.

BR27D card guide on reproduction SCELBI

The only cardguides that I could find that are still in production, are model BR27D from vector electronics.
http://www.digikey.com/product-detail/en/BR27D/V2027-ND/1886457

They are expensive, but at least they come in pairs. The screws for these guides appear to be size #4, not #6, like I had expected were used on the original SCELBI computers.