[exim] long retry times with temp. errors

Hello,
I have a slow pipe transport (may run several minutes) and returns an temp.
error (exit code 75) if too many parallel instances are started.

The retry rule is "*@partial0-lsearch*;/etc/testhosts * F,15m,3m;
G,16h,1h,1.5; F,4d,6h".

With exim 4.50 (Debian Sarge) the retry behaviour was ok, shortly (<=3min)
after a successful delivery the next attempt was started.

With exim 4.63 (Debian Etch) there are long delays (1h), if the message
stays >15 min in the queue. I suppose the change PH/19 in 4.61 is
responsible for that.

Questions:
1. Is it possibe to get back the retry behaviour of 4.50 with 4.63 (by
configuration change) ?
2. Is it possible to limit the number of running transports of one kind
without blocking other transports ?

Thanks
Guido