Hi ShawnD
With the vacuum feed trays the best method to feed #10's is flap open , with the bottom of the envelope fed as your lead edge . If you create a paper catalogue for a flap open envelope with a custom page size of 9.5x5.5 long edge feed , you will get good results , and good news is if you want to print on the flap, it can all be done in a single pass...... Yes you need to open and close the flaps, but most experienced press folks can whip them open and closed in short order, and most jobs are short run .... hope that helps . Maybe other point is you may need to design a file that is also 9.5 x 5.5 ( the dimensions with the flap open ) ... or I think you can use image shift and/ or rotate 180 to get a 4.125 x 9.5 file to print correctly....
Other good news on the 7100, if you do run envelopes, sometimes you will get fuser etching.... just run the Fuser Smoothing option after your envelopes and your fuser will be pristine again if you run a 13x19 poster as your next job...
If you go into the Master Paper Library, there are some generic envelope settings for various Gsm weights...... pick one, then modify for your size of choice. The envelope settings are typically optimized to reduce fuser roller pressures to eliminate creasing , etc....
Good luck ... also remember to run them face up ideally.... in your Fiery print properties, Finishing Settings ....Face Up Normal Order...
Cheers ....
Steve