Now, width at 50% of length is ideal. At 49-3/4 by 98-3/4 the width is 49.874% of length. That's less than 13/100ths of one percent different. How good do you have to be before that imperceptable difference in size starts to effect your game?
Even the best pros in the world wouldn't be affected by this. The difference is so minute, that any resultant effect on play could easily be passed off as being the result of any number of factors... Humidity, temperature, cloth tension, etc... But, people on this forum tend to be purists, and will often overstate the importance of this somewhat trivial detail. For what it's worth, I work on a LOT of pool tables, from a number of different manufacturers. There aren't many that measure an EXACT 2:1 ratio.
But back to my question. According to numbers from a recognized expert my cushion is where it should be in terms of nose height and top corner height. My only problem is that the K55 cushion is bigger than the Monarch cushion and pushes the nose 1/8" farther out onto the table, thus reducing the overall playing size 1/4". The subrail has two facets to it, the one that the cushion glues to and the one under that. Seems to me that all I need to do is to trim 1/8" off both of those facets which will move the cushion 1/8" away from the center of the table and give me the correct playing surface size. I've looked all over for a description of the subrail modification to use K55 cushions of an old Gold Crown and for whatever reason the people that do it seem to refuse to talk about it other than to warn about what a complicated procedure it is. I really can't see why it would be any more than what I have described here. I've been wrong before, and if I am here I would appreciate it if someone could explain to me how.
Check out this thread, for images of my tooling, specific to modifying Brunswick sub-rails
When replacing the cushions on any pool table, the most critical factor will be ensuring that the cushion is mounted at a consistent height. This is even more important than the actual height itself. That said, the easiest way to do that is by giving yourself a straight sub-rail. The factory Brunswick sub-rail height on your table would have been 1 23/32", with a nose height of 1 29/64". However, the top edge often gets belt-sanded, when the cushions are installed. That makes the top edge of the sub-rail a bit inconsistent. Now, when you install a set of cushions, using the inconsistent top surface of the sub-rail as your guide, the new cushion will be installed with matching waviness.
To avoid this, we knock the height of the sub-rail down to 1 11/16". However, doing so, will also drop the nose height of the cushion. So, we have to modify the sub-rail face angle, to accommodate the change in height. Since you are modifying the face angle, you might as well knock it back to get your 2:1 play area.
Once the face angle is cut back, you'll need to modify the lower angle. Now, here is where you could get into a bit of trouble..... Don't try to match the factory angle, as you will cut away a lot of the factory cloth relief area. You might think that this isn't a big deal, as you could always cut the cloth relief back further... Well, that is true. However, for rails that use the figure 8 nut plates, you'll have some trouble stapling your rail cloth, near those plates. Though, you could plan to upgrade the figure 8 plates with
Stafast threaded inserts, and avoid the issue altogether, but there is considerable work and cost associated with that.
In your case, the bottom staple area is wasted. If it were me, I would cut off the sub-rails, and replace them with new. I think that it's actually easier than modifying existing sub-rails, particularly when customers want tight pockets.
Images below for reference: