This is not really an answer to your queston, but a suggestion re getting
more water into your cat. Several people here posted that cats like
to drink water from a variety of places around the house, and that they
will drink more if you provide more watering places. I found this to be
true. We had two water dishes, one for each cat. We now have four
and judging from the way the levels go down between morning and
evening my cats appear to be drinking almost twice as much water
as they used to. Also, my strange little tabby loves the cold filtered
water that comes out of the fridge, out of the front of the door. She
waits for it like the other waits for food every morning, and drinks
for a long time. (FWIW my cats get wet and dry food.)

You're right.  Cats fed dry food drink about 6x more water than cats fed
canned food but their total water intake and turnover is actually less than
cats fed canned food.   Cats fed canned get over 90% of their total water
intake from their diet so they need to drink very little water, whereas cats
fed dry food get 96% of their total water intake from drinking but much of
that water is lost to fecal moisture.

The total free water intake (from food and drinking) actually decreases when
cats are fed dry food.  The water to dry matter intake ratio for cats fed
canned food is 1 1/2 to 2 times higher than cats fed dry food.  This is very
important for male cats who are at a much higher risk of urinary tract
obstructions than females.

It seems the male cat should be urinating a

Most of the water dry-fed cats consume contributes to fecal moisture -
that's why their urine volume is lower.

Maybe I should be rationing the dry food so that he can't get full off

Good plan.

Seems simple enough, but as

High water turnover is very important for male cats.  See how their urethra
narrows kinda like a funnel where it passes over the pelvis:

http://maxshouse.com/anatomy__urogenital_system.htm

http://maxshouse.com/feline_nutrition.htm#Water Requirements

http://maxshouse.com/feline_nutrition.htm#Dry Food vs Canned Food

Phil

We used to mix the two together. Might be a good compromise.

I think you're wise to be concerned. I have a male cat who also eats a
lot more of the dry food than the wet. I put out 3 different kinds of
dry food: dental diet, hairball diet, and urinary tract. He likes all
three.
I also use two water bowls. One is the drinkwell fountain and the
other is a plain water bowl. I serve them  (six cats) a saucer of
Lactaid per day. He will lap at it sometimes. My vet thinks our water
has too many minerals for cats and he recommends that they drink
bottled distilled water which I buy by the gallon jug. My guy has had
only one urinary tract infection so far and he's 8 years old.