Stacking Trade Routes?

How many ships can you stack on trade routes? i recently started a campaign as the british and randomly dropped 4 ships on one route, i was shocked that i got a massive investment back?
how had i not known this before hand?
seriously i've been playing through with 1 maybe 2 ships on trade routes!

anyhoo, how many ships can you stack on them? does anyone know the limit?
thanks
pete

i belive the limit is just the maximum size of one fleet

Yeah, you can have an entire fleet full where fleet size is determined by your game unit-size settings.

The return on the 'investment' does obey the law of diminishing returns - the more ships you have, the greater the amount of product available and so the traded price-per-unit drops. Also be aware that even if your trading fleet is bringing back say 50 units of product there might only be a market for 30 units. The spare 20 units is just wasted and those extra ships in that fleet are just reducing your profit (because you're still paying maintenance on them and over-supply brings down the trading price). Keep an eye on the trading tab and try to balance where your trading fleets are with what the market needs.

ooh good advice thanks!