Having a 3/4 stick hover in normal mode will allow you to switch between normal and idle-up anywhere above half stick without dropping altitude. If you have your normal mode curves set for a 1/2 stick hover, then at 1/2 stick you are around +5 degrees of pitch and about 50% throttle. Now, your idle-up curves are set for 3/4 stick hover which means 0 degrees of pitch at 1/2 stick and less than 50% throttle. Doesn't take long to see that if you're in a normal mode hover and switch to idle-up you'll instantly go from +5 degrees and 50% throttle to 0 degrees and less than 50% throttle. Without instantly raising the left stick, your heli's gonna drop.

Now for setting the throttle curve:

Make your adjustments to the linkages in normal mode. Set the left stick at center (half stick) and make sure your curves (throttle and pitch) are at 50% in the transmitter. The throttle linkage at that point should be at 90 deg. to the servo arm and the arm on your carb. The carb should be 50% open. Your collective pitch should be set to 0 deg. at this point by adjusting the linkages to the head.

Now you can set the pitch curve to +/- whatever for normal mode by moving the stick to the top and bottom and adjusting the corrosponding values in the transmitter. For a 5 point curve, you're pitch curve should be fairly linear and go from 0deg. at center stick, +5 deg. at 3/4 stick, and +9 or 10 deg. at high stick. The bottom half is similar, but you may not want -10 deg. at low stick in normal mode. You might go -2 deg. at 1/4 stick, and -4 deg. at low stick.

Now you set the throttle curve for normal mode remembering that you've already set the linkage properly, so all adjustments will be made in the transmitter. Your hover point is 3/4 stick, so the throttle curve point at 3/4 stick should be about %50 in the transmitter. High stick should be approaching %100, but you will need some flight testing to better determine the throttle opening required at full collective. Now, at half stick you have 0deg of pitch and very little load on the engine, so your throttle curve point for half stick might be about 30%. Low stick in normal mode is where you want a good idle, so set it idealy at 0 in the transmitter, but may have to be about %5. The point for 1/4 stick should be about half way between low and 1/2 positions. In this case, %15 to %17 at 1/4 stick.

Setting the idle up is easy now (providing you want to start out with the same headspeed in both modes). There are no linkage adjustments to be made, just points on the curves.

The pitch curve in idle-up is the same as normal from 1/2 stick to full stick. 0deg. at center stick, +5 deg. at 3/4 stick, and +10 at high stick. Below half stick, you want -5deg at 1/4 stick and -10 deg. at low stick. Done here.

The throttle curve in idle-up is the same as normal from 1/2 stick to full stick. %30 at center stick, %50 at 3/4 stick, and %100 at high stick. Below half stick, you want %50 at 1/4 stick, and %100 at low stick. Done here.

Now your curves look like this:

Normal mode

low stick = idle and -4deg.
1/4 stick = %15 and -2 deg.
1/2 stick = %30 and 0 deg.
3/4 stick = %50 and +5 deg.
full stick = %100 and +10 deg

Idle up mode

low stick = %100 and -10 deg.
1/4 stick = %50 and -5 deg.
1/2 stick = %30 and 0 deg.
3/4 stick = %50 and +5 deg.
full stick = %100 and +10 deg.

Now you can spool up, lift off, and hover in normal mode then switch to idle-up in a hover and fly off into FF, aerobatics, whatever.

Ben