hi, pretty new to the forum and modding guitars
So, my question:
How does the CS 69 pickups sound like with a clapton mid boost?

Welcome!

They'll hiss like crazy.

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+1

The only way I know that might "tame the serpent" is to wire up a dummy coil arrangement similar to the configuration used in the Deluxe Powerhouse Strat.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY

That'll work!

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so.. how is the "wire up a dummy coil arrangement" done?

I'll make this as short as possible, tailoring it to your application for a Strat where all the pickups have the same winding and polarity orientation such as with a set of CS 69s and where the dummy coil shall be active at all times.

A dummy coil acts as a 'noise catcher' for 60 cycle hum. It is a reverse polarity coil to that of another coil which it is teamed with. The only difference is, it will not have magnetized polepieces and therefore, it cannot 'pickup' string vibration. It operates under the identical principles of how a humbucking pickup works. Bear in mind though, to have an absolutely 'perfect' dummy coil requires some serious mathematical equations and coil construction, tailored to a specific pickup. So, just as in the "real world', no humbucking pickup is 100% efficient, obviously, the same holds true for any existing pickup destined to serve as a dummy coil.

Ideally for your dummy coil, you'll want to start by finding a pickup as close to the specs of whatever pickup(s) you are going to team it with. That is, shape, gauge of wire and DC resistance. It doesn't have to be a perfect match, "close" will do. The magnet(s) of this pickup must be able to be removed without damage to the coil. If the coil winding is exposed, it would behoove you to put tape around it to protect it. A good choice is an imported Strat pickup with plastic bobbins and ceramic rod magnets glued to the bottom of the pickup, butted up to the iron polepieces. Typically, the coil in these types of pickups do not come into direct contact with anything other than the plastic bobbins it is wrapped around. Back to the magnet(s): These magnets can easily be removed from the bottom of the pickup by pulling or prying them them off. Usually with these types of pickups, you can even remove the polepieces by pushing them out of the bobbin without damaging the bobbin and/or coil as well which brings us to you having the choice of leaving the polepieces in or taking them out. The difference is, leaving the polepieces in will have them act as an antenna, aiding in drawing the in line noise and killing it. However, it will raise coil inductance. In this case and in other words (over-simplified), it will kill more noise but it will take out more highs with it too by comparison. This can be welcome for many bass players who for example, have a P-J Bass. The P pickup is humbucking but the J pickup is not and by design, is oftentimes wished to have less highs and a tad more bottom end. The same holds true for Strat enthusiasts who want to get rid of the 'ice-picky' highs. So, it is relative.

How to hook up the dummy coil is a simple, "one-shot" trial and error as usually, the polarity of the dummy coil is unknown. In your situation, the dummy coil should be placed on a similar plane and same facing direction as the pickups. The lead wire from the pickup selector switch to the volume pot terminal is removed. Using alligator clips on each lead of the dummy coil, one end of one of the clips should be attached to the selector switch and the other clip's other end to the volume pot terminal where the aforementioned wire was removed. Naturally, the guitar has to be plugged in with the amp now on. Next is to listen for the audible noise and make a mental note of it. Then, reverse the clips on the selector switch and the volume pot terminal. One of these two hookups is going to be radically quieter than the other. It is this radically quieter of the two which has the dummy coil in reverse polarity and obviously, is doing it's job. Shut the amp off, remove the alligator clips and solder the two leads appropriately from the dummy coil thus making it permanent. Ensure that there is enough lead length from the dummy coil to secure it underneath the pickguard, typically between the selector switch and the pots again, on the same plane and direction as the pickups. Button, string and setup the guitar as applicable and you're done.

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The Elite Strat has also that dummy coil pickup beneath the pickguard.