Added flaperons to my Altech Pilatus Porter which has a 6' span, full length ailerons 1 1/4" wide, straight wing 10" chord. The flaperons make almost no discernable difference in slowing. It's a semi-symetrical wing. I am thinking about bolting on some 'extensions' about a foot wide to the bottom of the aileron and extending the 'flaps' portion an inch or so to actually give some functionality to the flaps. What do you think, would it work? Would it have any negative response on the aileron function. I am using a Futaba PA1 which does a great job of wing leveling.

Have you tried using spoilers instead of flaps?
I would recommend that you bring the ailerons up before you try modifying them.

Simply said, no, I hadn't even thought about it. Used spoilers on gliders to kill lift, wouldn't that be the same though? Would it slow the plane more in the 'up' position, and/or would it steepen the approach? Do they have a different effect on aileron function when in that mode? Since your familiar with them, I'm curious as to your observations. Seems like it would just as easy to program in. I've got the horns set a couple of notches forward for differential- would I change that?

I would try it. On my GP Giles, flaps do absolutely nothing to aid in landing. Spoilers let me come in more controlled, and less bounce. What I don't like is that with the Giles, if I have to abort, I cannot just go vertical, I have to build speed first. The spoilers provide a lot of drag.

After I started reading Andy Lennon's articles in Model Airplane News about 10 years ago, then later his book, "The Basics of Model Aircraft Design", I found this:

Flaps on symmetrical wings are pretty much a waste of time, although as wsmalley said, spoilerons may help. But you have a symmerical wing, and have the capability to GREATLY improve your takeoff and landing performance, with a little effort. If you like the plane, it's worth the effort.

Try slotted flaps, per Andy Lennon's articles. (or email me if you can't find them) Spanwise, the ratio should be about 60% flaps, 40% ailerons. Chordwise, the ailerons should be about 25% of the chord, and to avoid pitch coupling when you lower the flaps, they should be about 33% chord. It's not that much effort to add them, and they will give you performance that is much more scale-like for your Porter.

They're a much better solution than whatever you can do with strip ailerons and and mixing.