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The only time I've been able to tell a real difference in flight is between a very large (48) PC and no PC at all (direct bag). Truthfully, I think BASE canopies are probably big enough that the effect of canopy distortion on the flight and flare are going to be pretty minimal.

I did a litte math and here are the results:

At full canopy flight a PC will pull with the following forces:

~ 15 LBS for a 48"
~ 13.5 LBS for a 46"
~ 11.5 LBS for a 42"
~ 9.5 LBS for a 38"
~ 6.5 LBS for a 32"

That said I can only tell between a 42" and the 32" I use to for test jumping off planes. The canopy flares a bit better with the 32".

care to share what formulas you used?

If I'm not mistaken, a lot of the distortion on smaller skydiving canopies results from the fact that they are very high aspect ratio. This means it is much easier to pull the center of the canopy back with respect to the endcells, for example. Because a BASE canopy is relatively low aspect ratio, I wouldn't expect a lot of distortion even with larger pilot chutes.

For what it's worth, we were jumping a 111-foot span a while back and noticed that the canopy never really had a chance to start flying before we touched down. I normally use a 48" F-111 pc for backup on the static line, but thought this would make little difference from such a low height, and might make a difference in the flight characteristics. So I did one jump without the pilot chute. There was no noticeable difference in the degree to which the canopy was flying when I hit the ground.

I should also mention, Dwain later pointed out that most premature breaks occur fairly late in the deployment sequence, so he hypothesized that a pilot chute likely would be helpful as backup even on a very low object.

Michael

P.S. Edited for clarity.

I jump regularly with a jumper who weighs 120 lbs under a FOX 205. He uses a 48" ZP PC all the time with no problems.

The canopy never had a chance to start flying from 111 feet. No way!!