I refer to my post in my Wing Fell Off blog. I am now in the process of converting the Biff to FS2004. Unfortunately it is not all that straightforward as the implementation of virtual cockpits differ between the sims. CFS3 models to a higher vertex resolution. The FS2004 makemdl.exe exporter takes many many many minutes to export large models to FS and frequently decides to error half way through leaving one to guess as to the cause. On the other hand models export to CFS3 in seconds usually without hiccup. Thus one can check out mesh adjustments in game, relatively frequently
The bottom line for those waiting on the FS2004 Biff - don't expect it for a few weeks or longer - the model needs modifying as it was modelled with CFS3 in mind.
It may be more advisable to model the Sopwith Baby to FS2004 standards and convert to CFS3 than the other way around. I will experiment with that in the coming days. I have another WW1 model coming out of my mesh collection also for completion for FS2004. I will reveal that soon.