Double recipe advice...help

I love the NB Bourbon Barrel Porter Kit! However a whole L of Maker's Mark gets a little expensive! So what I want to do is brew two batches (one with MM and one with cheap stuff) so I can do a fair taste test.

So to the question:
If I have a large enough kettle can I just brew with everything doubles then pour 1/2 into each Primary?

Any other modifications I should make?

The Recipe calls to do the boil with 2.5 gal then add water after to get it to 5.
(However I usually boil with 3.4-4.5 almost a full boil)

Thanks!

I'm actually brewing that exact kit Saturday!

There was another thread on here about splitting up a 10g brew into two 5g carboys. I'm sure the same will work splitting up a 5g brew. Just fill up the first primary to the ~2.5g mark and then fill second primary. Mix wert well though before pitching.

I may actually substitute MM with a rum. Heard it's a pirate porter recipe worth trying. I like your idea though, I could go half MM and half rum... Interesting

I use rum in Porter a lot. I call it Pirates Porter. I didn't know anyone else had used that name.

As to the MM. Add the MM at bottling. That way you will retain all it's character in the bottle. You can then complete the batch as normal, and when it comes to bottling, just rack half to the bottling bucket with the MM and priming sugar, bottle that, and then rack the rest into the bucket with the rest of the priming sugar and the 'cheap stuff'.

I see no reason to use MM. Just use a bourbon you like. If you like it straight, you will like it in the beer.

Always add any liquor at bottling. There is no reason to add it earlier (unless you used it to soak some oak or spices in first.