@sdmf74Here's a guide:
1: You need to know the inside width, height, and depth of the enclosure.
2: You need to know the width, height, and depth of the lipo pack you are planning to use. Listed dimensions do not include the discharge wires and balance connector wires - adding 5mm-7mm to the height should provide a good estimate as to how much height inside the enclosure the lipo pack will need.
3: The DNA200 board requires 71mm in height, 18mm in width, and 12mm in depth inside the enclosure. If you're going to use an XT30 connector placed between the underside of the board and the lipo pack, you'll need to add an additonal 3mm-4mm.
4: There are various 510 connectors available that have various heights. Both FDV and Varitube list the total height of the connector. Use that height and subtract the enclosure's wall thickness to get an estimate of how much inside depth the 510 will require - and don't forget that the center pin moves down when screwing an atty on - you'll need clearance for that movement as well as for the wiring soldered to the center pin.
5: Using the known dimensions, draw it on paper how you want to place each part inside the case. It's customary to place the DNA200 board along the side of the enclosure with the lipo pack behind the board and the 510 connector above the board and lipo pack. Don't forget that Hammond enclosures have corner screw posts that reduce the available inside dimensions.