The Seastar Pro helm requires a balanced cylinder, which the Seastar front mount cylinder is and a sideram is not. However that doesn't necassarily mean a Capilano helm wont work with a balanced cylinder like the Seastar front mount one. What Burty means by to powerfull is that the Capilano helm pumps more fluid than a Seastar helm per revolution of the steering wheel. As the Seastar cylinder is alot smaller in terms of fluid capacity than the Latham and Marine Machine side ram type's a Capilano helm thats usually used with these sideram set ups would move the Seastar ram from lock to lock with far fewer revolutions of the steering wheel than the normal seastar helm.
However it all depends on the model of Capilano helm. The most common one is the 1275V which is adjustable between 2.7 to 5.4 cu/in of fluid per revolution. There is a 1250V Capilano helm to which is 1.7 to 3.4. The Seastar helm is depending on the model is either 1.7, 2.0 or 2.4. The Pro helm is 2.0 cu/in. So if its a 1250V Capilano then should work, if its a 1275V (like Burty's) just set it on minimum and it would be okay just a bit faster than the fastest normal Seastar helm (the 2.4). But if its a 1350 Capilano helm the forget it cus thats 8.0cu/in and not adjustable.
Gav I assume you are using the seastar front mount cylinder?