I made a woodfordes wherry kit for this xmas, with banana addition. Turned out very nicely, i mashed up 4 pound bananas and cut up half the skins,also poured some banana essence on,put them into a muslin cloth tied in a knot and poured boiling water over, i then suspended it in the wort for the full fermentation period about six days, agitating gently each day to get the flavours out.Racked and barreled straight off.
When i brought the pressure barrel in from the garage to the kitchen for serving it did take a while to clear after venting pressure about 3 days. Banana flavour was there big style, had also taken some of the bitterness off the ale for a more rounded flavour, went down well with everyone and lasted well about 8 days. I thought it was a success.
Doing with a kit it seemed a more viable experiment as if you had all grained and mashed, spent all that time and went wrong i would have been well ****** off, but for the cost of a kit and minimal hassle well worth it.