A few things to remember when building an FPV system. The screen needs to be able to be seen in bright daylight! Buying the cheaper option in this regard will come back to bite you on the *** later on! 7" is ok, going smaller than that is going to really effect how well you can see what's in the frame of the video . . . There is some 8" screen around too! Using a screen with less than 500 cd/
m2 is a waist of money
All in one screens seem great, until one thing goes wrong with them! Be it a faulty battery/receiver/LCD the whole thing becomes worthless! In my kit I have spare vTx and vRx as well as most "looms" I need for on my controller (LCD power, Receiver Power, DVR power, video cables). This enables me to swap out a component if I think it's faulty! I even have multiple gopro video out cables in case I damage one!
As for the DJI VTx, I don't own one, but I also have no interest in buying one, it's too bulky and a fan? For what? Unless your pushing 1w on a PCB that small you shouldn't need a fan! 600mw work fine with only a heatsink and antenna attached, the fan is only going to create noise along the power running the Tx, and if you incorporate a noise filter (inside the dji Tx) to limit the noise, with all the extras building up. . . It's become a big waist of space and weight . . . Two critical things on a helicopter!
And then to Finnish it off, they pack it in a large plastic/metal casing that can fit neatly anywhere? The bear or open style vTx's are usually covered in clear heat shrink to prevent shorting etc but also to keep down weight! They can be mounted inside the phantom with some creativity or easily mounted externally on the phantom with one of the thousands of CF mounting plates
Sorry for the crap pic (ipad2) but here is the latest mounting plate I'm using for my Vtx, take note at how the "hole" is designed exactly to fit the heatsink! Also take note at how close my 5.8 transmitting antenna is to my 2.4ghz receiver antenna?? I'm not sure if thats bad or not!
I'll admit, to get my set up to where it is, I've made plenty of mistakes usually in the name of trying to save money now I have a spare screen, antennas, Vtx VRx and god knows how many CF mounting plates (to suit tarot, Vtx, iso mount, servo gimbal) I might make a thread and list all my spares for someone else to make use of?? But now I've got it close to how I want it, the next thing I'll be looking at is reducing the weight (somehow!)