The Beta65 Pro frame is a great choice if you are looking into building a 1S brushless whoop - light weight and super sturdy. There is a small mod, that makes the frame even better. Referenced to as low pro or low profile mod, there is only little information to be found about this mod online, I thought I would share how you actually do the mod.
Before the mod, the frame weighs in at 3.77g. The mod shaves off a whopping 0.14g pushing the weight down to only 3.63g.
The battery is closer to the center of gravity and, in my opinion the most important improvement: you land on the motor screws instead of the battery.
A picture says more than a thousand words, so here is a comparison of before and after:
You basically remove the original battery holder and use the space between FC and parts of the battery holder. In the following picture you can see which parts you need to cut. I use side cutters to snip it, but you can also use your hobby knife. I then used a file to clean the edges up a bit, bit this is definitely not necessary.
When it comes to mounting the flight-controller, you have two options, you can either mount it in such a way, that the USB port is on top, under the canopy or accessible on the bottom.
The preferred and most light weight option is to mount the flight-controller upside down with the USB port on the top - under the canopy. In this case you can use the short grommets. Do not forget to flip the board within Betaflight. You might also need to remap the motors in order to keep the wires as short as possible.
If you want to have the USB port accessible it is essential to have the right rubber grommets. A lot of flight controllers come with the short ones, where the slit for the FC is in the center of the grommet. In order to keep the USB port accessible we need the grommets, that are longer on one side, otherwise the USB port of the flight controller will block the slot for the battery.
I tried different grommets and in my opinion the once linked above are the easiest choice because you get grommets and the matching screws. If you are a perfectionist, I suggest getting this grommets. They are long enough to get the job done, but not as long as the ones that come with the crazybee board (of course you can just shorten those…). Sourcing the matching screws could be troublesome though. I was lucky enough and the screws that came with my BetaFPV FC were a nice fit.