I use almost no negative pitch in my moving loops. Diminishing positive pitch up to the top (lots at the entry, little at 1 qtr through), then neutral at the top and on the 3rd qtr back down, then increasing positive as it gets into the last quarter of the loop to try to stop descent at the same altitude I entered. On a normal flight more the pitch won't be the issue, it will be throttle. On a normal pitch curve you will be 50-65% throttle at the neutral pitch position (mid stick), and then as you enter the bottom of the loop and start applying positive pitch it won't have the headspeed needed so you will have to really push it if you come down the loop too fast. This will be especially bad if you have a 0-60-60-60-60 type normal throttle curve and are not running a governor setup, since it will not even try to dial up the power you need to level out at the bottom. You can do it, but I'd recommend starting out high and you may want to make sure you're running a 0-50-65-85-100 type normal throttle curve to make sure you have power at the bottom if you need it. Also, make the loop big. Big loops give you lots of altitude to work with and they bleed lots of energy on the up swing. If on the down swing you get nervous or you think it is getting too fast you can simply pull back a little harder on the cyclic stick to prematurely level the heli out of the loop, and apply positive throttle/pitch to stop decent. With the altitude of the big loop, even if it is underpowered you will have plenty of time level out and stop the descent.
