Steve,

You could use the same prop, but, often in electric conversions, we prefer to use the largest prop that clearance allows unless it's a scale plane.

The flight times will average around 7 minutes depending upon how hard you fly. The Seamaster is very aerobatic!

I would check the battery temperature after the first couple of flights. The longer you fly, the warmer the packs will likely get. I have always wanted to convert a Seamaster but just haven't done so yet.

If you use a Jeti 77-amp Advance PLUS ESC, you won't need to worry about cooling it.

As for the charger, to charge the 6s configuration as a whole, there still are not many choices other than the AF Lithium 109. Simply remember to always watch the cell count in Mode 1 (first 3 minutes) and always spin that darn current knob to minimum before starting a new charge cycle.

If you split the packs back into two 3s packs for charging, buy two of the [link=http://www.hobby-lobby.com/chargers_lipoly.htm]ETC2500[/link] chargers that work on 1-4 cell packs.

The fact that you know what questions to ask means that you already have good knowledge about electric flight.