yeah, it all depends on how much power you want it to have, 300 watts for a 4lb bird = 75w per lb, and that is getting a bit on the low side, but it might work if you just want to put around and not do anything too terrific. Is the 4lb the AUW with all the servo's batteries and other stuff?

you can also try this
http://www.commonsenserc.com/page.ph...tor-wizard.php
http://www.commonsenserc.com/page.ph...ent_chart.html


also here is a better list for you as far as w/lb http://www.horizonhobby.com/Articles...563&tag=aq_art

We can determine the power requirements for a given model based on these Input Watts Per Pound Guidelines (using the RTF weight of the model, including battery pack):

• 50–70 watts per pound: Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models

• 70–90 watts per pound: Trainer and slow flying scale models

• 90–110 watts per pound: Sport aerobatic and fast flying scale models

• 110–130 watts per pound: Advanced aerobatic and high speed models

• 130–150 watts per pound; Lightly loaded 3D models and ducted fans

• 150–200+ watts per pound: Unlimited performance aerobatic and 3D models