This is from the MegaSquirt rotary engine community.

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Mike Robert spent some time on a dyno last year and was able
to test what happened in the case of stock 'spilt' spark timing,
trailing only, leading and trailing firing simultaneously
(no split) timing and leading only timing.

The results were:

* Leading and trailing spark in a roughly stock timing split
configuration gave ~164 RWHP @ 8500.

* Trailing spark only only ran very badly (as expected) and
power was way down, EGT was high enough to make the exhaust
medium red; that run was aborted.

* Leading and trailing spark firing simultaneously were
no different from stock split until after 6500 rpm or so;
even then the difference was almost negligible.

* Running leading only spark produced about the same
power as well, within error margins.

All of these tests were run with 26 degrees leading advance
max on 87 octane pump gas.

However, idle and low load emissions might be better
running both Leading & Trailing spark with split timing.

http://www.megamanual.com/v22manual/rotary.htm

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A lot of this fuel injection stuff is for stock side port
engines with stock intake manifolds so it has some application
problems in our case. Sorting all this out for a 250 HP P-port
engine would not be a trivial matter.

There is some interesting info in here on staging.

Paul Lamar