I got a Brooks B17 narrow right out the door on my Surly and something felt very wrong from the start. Finally I realized I was sliding forward to the nose, I adjusted it some, a few times...until it felt better but still I was sliding to the front. So today, I looked at this website and used it as a guide to help me adjust my saddle. It turns out it was the fore/aft position of the site; boy, did that make a difference! Now I know why Brooks has the reputation it does.

Here's the site I used:
https://www.jimlangley.net/crank/bikefit.html

A lot of you probably already know this information but it's useful for any noobs, like myself, to find the optimal position for their saddle. It takes a lot of time and patience but it's worth it.

I usually just try to get the seatpost lined up about the middle of the saddle. I take a level and make sure the bubble is dead-center. This seems to give me a pain-free positioning.

I also have calculated over many trial and error sessions, that the top of the saddle should be 27 inches from the center of the bottom bracket. (At least, in my case.)

yea, much trial and error goes into finding just the right position for your saddle, but the fitting can be much more encouraging to ride in.
I found these two suggestions most useful. They look like mouthfuls but if you read it slowly, it isn't that complicated and the instructions seem pretty fool-proof for new riders.

Find fore/aft seat position: This adjustment requires a helper, too. Place your bike on a level surface next to a wall or post so you can hold yourself upright (or put it on a trainer, but be sure to level the bike). Put on your biking shorts and shoes, get on and pedal backwards until you’re sitting in the “sweet spot” on the seat. Move your feet into the position shown in the photo. The forward crankarm and pedal must be level with the ground. The fore/aft seat adjustment is correct when a plumb line (any piece of string with a weight on the end) hanging from the bony protrusion just below your kneecap, bisects the pedal axle.

Adjust seat height: The easiest do-it-yourself seat-height adjustment is done on a trainer or indoors in a doorway and requires a friend or spouse to help. Put on your cycling shorts and shoes, mount your bike in the trainer or place your bike in the doorway, get on and hold onto the doorjamb to support yourself. Have your helper stand behind.

To find seat height, place your heels on the pedals and pedal backwards. You’ve found the optimum seat height when your legs are completely extended at the bottoms of the pedal strokes with your heels on the pedals (photo A). Have your helper watch for rocking hips, the sign that the seat is too high. Now, when you’re actually pedaling, you’ll have the perfect bend in your knees (photo B).

Notes

This is a starting position. If it feels too low or high, adjust the seat up or down. But, only slightly to fine-tune the adjustment.
When you’ve found the perfect position, mark it with an indelible marker (or wrap electrical tape around the post to mark it) so you won’t have to go through the fitting process again.
Consider memorizing the measurement, too (measure from the top of the seat to the middle of the crank).

Wow, that's a lot of good information. I was lucky enough to have a pretty helpful guy at the LBS when I bought my bike. He helped me get everything situated and I marked where he had everything set so I could fiddle with it and get it back into the position he had it in. I guess I was lucky to get a good fit on the first try though.

I find brooks especially are very sensitive to seat position. Small adjustments fore/aft or angled up or down make a tremendous difference in comfort.