Thanks for reporting!Now on my own 3DS at my own house, using 1.2.1 with FBI 2.0.5, I'm getting 400 KBps, definitely the slowest I've gotten through wireless transfers. I'm not blaming you or anything, just hoping to report my test.
So I'm installing a 2.4 GB CIA and it took an hour and a half to install it at 400 KBps the whole way through.
Glad I can test it though!
That's the reason I put the Legacy Mode in there. It's way faster. I tried the same tweaks I did to the original transfer method, but the max speed I'm getting with the FBI 2+ compatible method is 700 KB/s roughly. While I still get 1200 KB/s with the old method.
I would say it's, in part (not blaming FBI), due to that FBI now writes an Integer value (ack) so that the PC client reads it to know if FBI is still up. It sends the value on each data package. However, I disabled the ack read from SocketPunch, but it caused failed installs when reaching 100% in ver 1.2.0-beta. I'm already testing if there's a way of getting more speed.