Problem with transaction CUNI and configuring decimal places

Question

Note: I'm actually an ABAP programmer and do not know almost anything about SAP configuration.
Note2: Sorry if this was posted in the wrong section. I am trying to avoid an ABAP solution so I did not post this in the ABAP section.
Note3: Sorry for cross posting. I'm trying to make this visible to as much experts as possible.
\[Problem\]
I'm tasked to increase the number of decimal places that a certain standard program in MM accepts.
\[ABAP solution I'm trying to avoid\]
The consultants' initial recommendation was to make Z copies of the standard table and the standard programs that references that table. This would be rather dangerous as there is the risk of missing certain parts of the code If I was to replace all occurences of the old standard table with my custom Z table.
\[Standard solution I'm trying to do\]
Now I've read several threads here that makes use of transaction CUNI to adjust decimal places of certain units of measure (see Re: Unit Of Measure problem and change decimal places in PO quantity). However, when I tried it, It does not work the way I expect it to.
In SE11, I created a custom table that has a quantity field (length: 13, decimals: 3) and a unit field (length 3)
In CUNI, I created a new ISO code TST (for test). Then I created a new Unit of measure ZTT (ZTesT) which makes use of my ISO code TST. I set the decimal places to 6.
When I insert data into my custom table, instead of 6, the number of decimal places remain at 3.
Please help in adjusting decimal places without touching the table.

Answer 1

Hello Dzed,
I've read several posts that suggest transaction CUNI to adjust decimal places in standard unit of measures. What I tried is a simplified simulation of what is needed.
In a more realistic sense, consider table VBRP and column FKIMG. What If I want to store items in VBRP and allow 6 decimal places for FKIMG but I am not allowed to modify the table? Is making a Z copy of VBRP the only solution? Or is there a more standard way of doing this?
My worry is that If I copy a table, I also need to copy the programs that use it and modify them accordingly. Our Basis do not want the standard tables touched.
Kyle