Making a pickup route deeper

[slinkp]

So, I've got this guitar (yes, a guitar... not a bass... I have sinned) which I love except I'm not satisfied with the bridge pickup sound.
It's a really odd shaped pickup. It's a Danelectro 59xt with a "dual lipstick" humbucker in the bridge.
Nothing else is quite the same size ...

I had the inspiration that I could have a custom pickup ring 3D-printed and try out some other pickups if I can find something that's small enough for the route, and avoid having to route the guitar.
A little measurement proved that either a Filtertron style pickup, or a P90, or a mini-humbucker should fit, given the right mounting ring.  I went ahead and ordered a Filtertron from TV Jones, and designed and printed a pickup ring. Everything seemed to fit and I was excited to install it ... tried putting the strings on and...

Crap. I forgot to measure the depth. The strings are touching the pickup!
The existing route shape is wide enough, but not deep enough. Looks like I need to go maybe 3 or 4mm deeper.

So, I need to either give up, or, make the route deeper.
I've never tried making a route deeper... I don't have any suitable tools... since I'm going to have to buy some tools if I want to proceed, what should I look at?
I don't have a workshop, just my bedroom, so it needs to be somethign I can just put away in the closet. No drill press here.
Can this be done by hand with a sharp chisel?
Dremel?
Plunge router? I don't have a template for this pickup nor how to make one ...

I'm ok with it not looking cosmetically great, since it won't be visible under the pickup and mounting ring.

[amptech]

Dremel + router kit (if this is a one off job, a $10 chinese dremel would do the job). Of course, the easiest would be to wind a pickup that fits🙂

[Dave W]

If this is typical Danelectro construction, wouldn't cutting deeper compromise the back of  the guitar structurally?

[Grog]

A couple years ago, I cut a pickup pocket .187 deeper using a cheap mini router purchased on eBay.

[Basvarken]

If you use an undeep router bit with ball bearing copy ring, such as the blue one in the picture, the cavity itself will be your template.

[Alanko]

I bought a cheap Katsu branded router for this sort of work. I use router bits exactly like those in the post above mine!

You can make fancy templates out of MDF or use scrap wood to make basic fences.

[slinkp]

If this is typical Danelectro construction, wouldn't cutting deeper compromise the back of  the guitar structurally?

I do need to measure to get a clear sense of how much room I have to play with, but it looks like making the (fairly shallow) route a bit deeper should be safe.
It's not built quite like the ones you are probably thinking of - those old ones, and my silver sparkle DC bass circa 1999, are mostly air between a thin pressboard front and back.
This one does seem to be still made of pressboard on front and back, like those; but in between is a fairly conventional solid body, albeit glued together from several layers of mystery wood, probably something cheap.

I'll take better photos if I go further - I started making videos too, to document the project, before I hit this obstacle -
but here's a couple shots of how the strings currently sit on the pickup (ouch), the wood visible in the control cavity, and what the pickup route currently looks like.

[slinkp]

Hmm, only one of the photos attached... Here's the control cavity:

[slinkp]

And here's how the pickup currently sits 

[slinkp]

Thanks for the advice everybody! Those bits look pretty cool. That gives me some ideas what to research!

I'll keep you posted. At my usual pace, maybe I'll get around to it in 2023