Valve size question

I found a great deal on a 15gal aluminum pot ($50!) and I'm pretty sure I'm going to buy it. I'll be using it as a mash tun (but not lauter tun) and a boil kettle. I'll want to install a ball valve on it because it's difficult enough pouring a full mash from my current 8gal pot into the lauter tun. I need y'all's advice on what size valve I should install. I'm probably going to go weldless but I'm open to suggestions. My LHBS sells a weldless setup with a .5" valve, and it can also receive a barb nipple.

Main concerns:

1) I figure that once I'm done with the mash, I'll lift the pot to an elevated surface, open the valve, and let as much of the mash run out into the lauter tun as possible. Even if I can only get half the mash out easily, that'll still take the load off and I can lift and dump the rest into the LT. So the real concern is clogging up the valve with grains. Keep in mind I'll be able to stir and poke around while draining to the LT. Will the .5" valve be big enough?

2) After emptying to the lauter tun, this kettle will then receive the runoff, and go back to the burner for the boil. I'll be chilling with an IC, and then running from the pot to the fermenter. Are hop clogs a big concern here, especially if I get a good whirlpool going with my spoon? I usually use pellets but not exclusively. Will the .5" valve work well here?

3) Finally, can I use vinyl tubing to drain from the pot? Obviously post-chilling is fine but what about post mash? I mashout to ~168*. Would I need to get some stainless tubing for this part?

I'd appreciate any advice or other recommendations.

I think a 1/2" valve is going to clog with grains going through.

Hops will go through after the boil is done on a 1/2" valve.

I suggest you make your mash and lauter tun the same vessel if at all possible. If not then put a stainless braid in the mash/boil kettle and loosely screw it in so you can undo it for the boil.

If you use whole hops a braid will work in the boil kettle as it will set up a filter bed for the break material. Pellets will clog a braid.

The vinyl tubing will work but will soften at those temps. The braided vinyl tubing will hold up better.

I suggest your use one vessel for you mash and lauter tun also. Use a false bottom or manifold in the bottom of your mash tun. This will ultimately make life much easier for you.

The valve will probably plug up with grain and the barb fitting will be even more of a problem than the valve in that respect. I'll second (or third) the suggestion to use a false bottom, screen or braid. I would use only the single kettle for the mash and lauter. You could collect runoff in multiple buckets. When you finish the lauter, you can clean out the kettle and use it to boil the wort. I used this method when starting out with all grain. I had only a single 10 gallon kettle with a false bottom at that time and it did double duty as a MT and BK. That worked very well for me until I moved up to 12 gallon batches and needed a larger BK.