Can I funnel the output of a portable air conditioner to direct it?
The manufacturer would clearly say no! His blower is designed to deliver air into an unobstructed space. The squirrel cage blower wheel in the standard furnace is designed altogether differently. It is designed to push against back pressure. The blower in this type of unit is not designed to do that.  

Additionally, you will knock all of the design parameters out of wack.  You could dramatically shorten the life of the compressor. You will definitely loose all of your warrantee coverage. 

An accepted solution would be a through-the-wall fan to move the cooling to another room, preferably placed lower on the wall. Or use a breeze box set in the discharge path of this unit, not too close, to augment air flow to the immediate area.