Mark,
Just after I sent the post I realised that junior member ment something else. I guess I need to read the rules on this site, (not likely).
I am using elevons on mine As far as the bottom of the plane I know that Larry felt that he didn't get it quite right but I am not that far along to discuss the contours. I think Larry is using spring airs that are modified to air up and down. His latest one is being set up for a turbine. If you ever see his planes up close they are abosolute works of art he really puts a plane together well.
I don't know how well your other fans will match up to the existing duct but if the Dynamax fits and the Picco .80 works well i think that would be my direction.
Others will have to tell you how the picco runs if you haven't run yours.
If you get a chance to talk to Larry it may take a while for him to warm up to you, I guess a lifetime of talking to 9 out of 10 modelers who are tire kickers and not serious about models have made him a little warry. I wouldn't discuss the merrits of BVM VS JHH either. I think one being in Fla and the other on the left coast is almost too close for their likeing.

Sparky