It is more important that you have unrestricted flow into the cistern.
Cistern no gutters.
Install standard size mesh gutter covers over the entire gutter that will lead into the cistern.
Cistern covers are 2 x2 and are cast in the floor.
Screwed connections are stronger.
I chose to use 2x6 material because i had it handy but if you choose to u.
This is a cistern i made from some pressure treated 2x6 material and a 55 gallon plastic juice drum.
Sweep all debris from the roof and gutters leading to the chosen downspout by using a broom.
I got the used drum locally for 15 and the wood came from my scrap bin.
This technique is usually only used when there s no fascia board.
A system of gutters and downspouts directs the rainwater collected by the roof to the storage cistern.
Remember that the x section of a 4 pipe is twice that of a 3 pipe.
The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel.
The cistern typically located underground may be constructed of various materials including cinderblock reinforced concrete or precast concrete fiberglass or steel.
Traditionally this involves harvesting the rain from a roof.
K style gutters can be spiked or screwed to the fascia.
If you join too many downspouts before they enter the cistern you could have a constriction that would be problematic.
Another method calls for gutters to be held in place by straps fastened to the roof.