Keel stepped? For and aft lower shrouds? And you say the backstay is not adjustable. But there is a turnbuckle, right?

I would think rake and bend are setup together...

Keel stepped w/inline shrouds. No apparent adjustment on the step. Don't know that I need adjustment there. It was not clear that bend and rake are set together. I would think rake is fore aft stay adjustable and bend is created with backstay tightening with either a Babystay or a forward lower shroud helping the bend get started.

Backstay is adjustable of course but not underway.

The bend will be induced at the partners. If the masthead is where you want it, rake, then adjusting the mast forward in the partners will induce some bend. I wouldn't use the baby stay as the principal way to induce bend but rather the combination of the mast step, partners, forestay, and backstay. The baby is more to prevent pumping in rough weather...for stability...in my usage.

If the mast step is not adjustable then the partners must be adjusted, and vice versa. My current setting is a bit weird because the partners has the lower third of the mast slightly bent forward. Not much but just enough to bother my eye when riding up in the dinghy. Something got goofed up last time the rigging was replaced as there is an extra toggle in the forestay, too. Other than the annoying lack of aesthetics everything is perfect.

Is the baby stay adjustable? With in line shrouds it's the only way to induce bend unless you've got a very powerful (hydraulic) back stay and/or a bendy rig. If the step is adjustable then you might be able to prebend by using the partners as a 'fulcrum' as you pull the masthead aft to set rake.

The luff curve of your main is going to dictate the amount of prebend you want/need.

I have some work to do, after running out of adjustment on the backstay, I took a couple of turns on the headstay (furler) now I need to start from the beginning and measure the rake if the headstay needs to go out then the Backstay may be too long.
I need to see what the arrangement is on the partners. I could pull the boot up and see how its assembled but I'm not ready to pull the mast right now and the boot is leaking just a bit and I'm kind of afraid of making it worse.

It has a turnbuckle, but not adjustable underway like C&C does with the short track to pull it out and tension.
My view is a downwind tension on the headstay and a straight mast (with the right rake), then get the bend with a backstay adjuster enough to flatten the Main. A new Mainsail is a need not a want right now and I want to work all the rig geometry out so I can get the cut right.

You can easily check if the partners are reasonable. Good chance they are. Slacken all the stays. If there are fire/aft lower shrouds slacken them too, but count the turns. Observe the mast straightness...just for a starting point. It should be fairly straight. Then apply some backstay tension while easing the forestay until some moderate bend is induced. Is the rake reasonable? If all looks reasonable then the partners and step are in a good place. Tighten everything back up in such a way that the masthead and bend and rake don't change much. If all is not good with just a little backstay tension then something will need to be done at the partners or step. If nothing is done the mast will not have a continuous bend from step to head but two bends. That cannot be good.

In a perfect world the mast is tuned without the fore and aft partners in place. When tuned they are inserted without changing the mast position. That's my method anyway. The step is adjusted to keep the mast reasonably centered in the partners, or perhaps for some other effect...such as my predicament as described above.

Do you use an adjustable backstay or just set and forget it. Do you race, I do some clubbing and a Bay race or two but may want to do a lot more if I get my rig right.

My backstay is hydraulic. On this boat the backstay adjustment is mostly for headstay tension. Pumping it on does bend the mast, of course, but that bend is usually mostly removed with the runners to give the main some shape. But whatever it takes to get the job done...that's my principal rule. I race and cruise. Cruising is not lazy for me. Always optimizing performance and comfort.

I have the mast setup so that with the backstay off, baby off, runners off, not sailing, there is about 2 inches of prebend in the 60 feet of mast above the deck. The aluminum section is 8" deep. Then while sailing I adjust things as appropriate. 2" of bend gives a nice full main luff. No bend makes the luff a little too loose. More bend, maybe 8", a full diameter, flattens the main nicely, like a door, more so at the top. The conservative limit is 1.5 diameters, 12", of bend. I have the hydraulic cylinder set so that with no runners on I cannot go much past that amount of bend.

I went up in the bosun chair and measured the static bend at three places. The sailmaker uses those measurements for the sail. It is a truly beautiful thing when done right.

The babystay is really just there to hold on to while on the foredeck It doesn't seem to do anything for bending. My spar builder agrees. It is rather an old fashioned thing, however is handy when bashing thru seas. Especially with bare poles or no wind.

Are your stays inline or spread for some aft support. I suppose the mast just wants to bend that way? so pulling on it just makes it bend. I've also heard the Baby Stay helps keep the mast in one piece with heavy spinnaker loads. Yea or nay on that.