Machining Aluminum Parts?

I recently ordered an aluminum print, and am wondering if I should have ordered a test piece first. Two things need to happen to this part after I get it:

1. I need to drill some holes. I placed starter holes and will drill them out to size
2. I need to machine a pocket in the top (think watch case, because that is what it is) to receive a glass crystal. The dimensions need to be exact, both diameter and depth

I'm not too concerned about #1, but I'm worried that the bonds between the powder will not be strong enough to be machined with a boring head.

I have access to three kinds of machines:

1. High precision CNC mill
2. Bridgeport mill
3. Lathe

I think the CNC is my best bet as I can take minuscule amounts of material off and it will mill a precise amount, but I don't know how to index the case. This is by far the most dangerous in the sense that the machine is totally under software control and it could do something wacky if I screw up somewhere.

I know how I'd do the operation on the Bridgeport (boring head), but I'm worried it will damage the part.

I feel like the lathe is best suited to this process, but the amount of support I can get to set it up will be limited.

Any ideas? I was thinking if I could encase my part in machinable wax it would give it some rigidity, but maybe I'm overthinking things.

To mount it in a lathe, couldnt you print, in a cheaper material, a unique collet in the negative of the part to securely hold the piece to turn the mating surface for the crystal? Perhaps the professional plastic material which I believe has good mechanical properties.
IIRC, the aluminum is similar to the steel prints in their construction. I have seen people who could machine the steel parts so aluminum shouldnt be much different.
For something like this, I would not go with CNC as the risks with programming around an already complex part outweigh any guaranteed accuracy from the computer.
But thats just my 2c.

The part has a hole in the center, so a bolt with washer should be able to hold it down. As for reinforcement, I didn't think about it but I probably could print a negative in PLA, using a large nozzle (stronger walls). I could check to see what a professional plastic part would cost, shouldn't be much, but I can probably print a big strong part in PLA/PHA.

I agree with the CNC assessment. The geometry is simple enough to program around, but I know I'd mess something up.

I did the following operations on my part:

Drilled holes to size
Tapped (M1)
Faced a side with a mill (1/8" bit, 1,400 RPM)
Turned an opening to a precise diameter (1,000 RPM, 0.005" per pass)

Build thread here:

https://forums.watchuseek.com/f6/tapered-case-impossible-design-4903809.html