Trading a portfolio of multiple systems

Say that you have 20 different profitable systems/algos that you want to trade.

1) Is it always best to combine these into one portfolio and allocate capital to that and trade?
You would of course do OptimalF allocation of capital between your algos/assets that you trade (or similar).

2) Looking at the different Z systems Zorro offers, is there a reason they are split in different systems? Most Z systems seem to have multiple algos grouped together under one.

3) Anyone know about further reading on this subject? Books, articles, blog posts etc.

It depends. When systems exploit very different inefficiencies - for instance, Z5 and Z12 - it makes sense to keep them separate. This way you can stop one system, for instance Z5 when the SMB lifts the price cap, and continue the other system.

Ok, thanks.

Is the separation good only for the ease of starting and stopping?

If you could start and stop an individual strategy inside a portfolio, would capital allocation/money management benefit from this?
(With a portfolio I assume all strategies in it shares one pool of capital)

1) in my opinion - yes, as long as you are going to seek for an overall performance maximum, by tuning capital allocation between strategies, based on past data - Vince's OptimalF vector, with 20 elements in your case. An extreme example: a strategy is a slight looser on it's own (big winner from time to time but far too many small losses in between); However, in a portfolio, it might improve the overall performance, having it's big winners just when you need them, when others loose. How much capital to allocate for this looser-alone-but-portfolio-improver? OptimalF is the answer. Using OptimalF still does not exclude decisions like taking out grid a system manually if SMB gives up, you don't have to wait until its OptimalF drops to zero.
3) My favourite books on subject are: R.Vince ISBN 0-471-75768-3 ; Jaeckle, Tomassini ISBN 978-1-905641-79-6 ( mentioned here )