correct spacing for slits in tun manifold?

i have not decided if i'm going to use slits or going to use holes yet. this is a diagram of my setup. i'm using a 5 gallon round cooler. i need help designing the slits/holes in the manifold so that i don't get stuck runoff. i'm concerned because i only have four different 4.25" runs that will contain the slits/holes.



i read the webpage about palmers design strategies, but it didn't answer these questions:

SLITS
1. what's the spacing between each adjacent slit?
2. how far thru the tube should i cut? half way? a quarter of the way?
3. how thick should the blade be? hacksaw? dremel cutting disc? grinder cutting disc?

HOLES
1. i've already heard it suggested that 1/16" or 3/32" drill bit should be used
2. how many holes do i need to drill in all to be safe from stuck runoff?

any other advice you have about cutting the manifold slits/holes is welcome. thanks.

Subscribed - I was about to post the exact same questions!

i tried to research this answer, google and brewtalk and youtube, before i posted a new thread. i just realized that "spacing" was a good search word, and i found this. https://www.homebrewtalk.com/f11/cooler-manifold-slot-size-spacing-61815/

i used CPVC and this guy used copper, but he said he did a slit every 1/4" with a dremel cutting disc and the cut was cleaner than a saw. if it melts the plastic, i will use a saw.

i'm going to try to minimize the amount of liquid that gets left in the bottom of the tun when it is drained by cutting slits in the bottom of the manifold as opposed to the top.
i'm also going to not cut too deep into the manifold, because when the water level drops and you start getting air in the slits, your tun stops draining. i'm not going to cut more than 1/4 of the way through the pipe.

i'm also going to soak hot water in the cooler for a couple of hours, then drain it through the valve, and measure how much water gets left undrained in the bottom.

More slits are better than less. 3/8" apart would be ok. Depth should be about 1/4 to 1/3rd of the way through, thinner the better. Make sure you have tubing on the output when draining.