Sizeing of CAP is always a big task for a tech/ engineer.
I can suggest you a better option ,which Iam doing since
very long with high success rate! Every one can try no harm .
ITEMS REQUIRED,
1, Needle valve 1/4''.
2, Guage 100 psi is ideal with 2 hose manifold.
3, Compressor with a constant pressure out put.
or nitrogen cyclinder with max 150 psi regulator.
4,Must know required suction and discharge pressure
of the refrigerant and application.
5, cap- for low temp appliction---.031''
medimum " " ----.050''
high " " ----.064''

HOW TO START WITH.
Connect every item of the application other than capillary, connect needle valve instead of capillary, vaccum and dehydrate the system,fully open the needle valve , charge the gas slowly,start the unit , check suction and discharge pressure, and get it to normal by adjusting the needle valve, for high Temp R22 suction will be 72psi and 300 psi discharge at 35c ambient, check cooling efficency for optimum level,
Switch of the unit , LET IT cool down to ambient, it may take few hours,
Restart the unit, with out touching the needle valve,
pressure and cooling should be same ,if any difference ?adjust needle valve slowly and charge required gas.
Repeat it again till you get same pressure & cooling always
Now take out the gas and save it properaly to reuse,
Remove the needle valve with out touching the knob of the valve,Connect discharge of the compressor or nitrogen cyclinder regulator with guage and in the out put of the guage connect needle valve one end and open to air other side, start compressor you will get some small reading in guage , take reading , put off the compressor ,again restart , some small changes will be there in reading, take average of the both the readings,
Now remove needle valve , connect cappilary and cut it to
size of the average reading. put off and restart you must get same readings , It will work perfectly!
DONT THINK OF CONNECTING NEEDLE VALVE PERMENTALY , INSTEAD OF CAP, IT WILL NOT WORK PROPERALY , BECAUSE ORIFICE OF THE NEEDLE VALVE WILL CHANGE DUE TO SCALING DEPOSIT.
WISH YOU ALLTHE BEST.
kind regards,
beni joseph.