Are you talking about space velocity? I would assume you are trying to design a pre reformer reactor and have some L / D concerns. I checked my reference manual, The Catalyst Handbook, by Martin Twigg, which is generally a very good syngas reference, but my edition doesn't have anything on pre reforming. I don't know if the new editions have anything more.
For pre reforming you will probably need to go to the catalyst manufacturers (Johnson Matthey, Haldor Topsoe, Sud Chemie, or Unicat. They can give you their recomendations for the latest high acitivty or shaped catalysts.
