My experienced suggestion is TWO feedlines AND put a duplexer on EACH feedline (only using one side of the duplexer) at the antenna end as filters. This way, you can add a preamp at the antenna later, if needed. (radio > coax > (preamp) > duplexer > antenna)
The reason for this is 1) the duplexers will help filter out the transmitter signal, both broadband noise AND 2m third harmonic when on V/u birds (the 2m uplink third harmonic falls very close to many uhf passband downlinks, SO-50 for one), 2) if placed between a preamp & antenna, the preamp will not amplify such noise (as opposed to having the filtering back at the radio) and 3) separate feedlines will help prevent the transmitter to receive interference
and allow the use & powering of preamps through the feedline.
That said, many use a single Elk or Arrow to work satellites. If it is handheld and the coax is only a few feet, not a problem. Even in those cases, whether I use an Elk or an Arrow with a built in low power duplexer (I have two of each), I still have a duplexer just before my rigs to help with filtering. (I also find manipulating a single coax so much easier when handheld.) BUT, when you move the antenna out into your garden, the much longer coax is going to introduce loss on UHF downlinks. This is where a UHF preamp is a huge advantage. And you also need to consider, that unlike with handheld operations, the polarity of the antenna will be fixed. This will, at certain times during the pass, introduce a serious loss of signal. It is not an end of the world issue, BUT be prepared for the periodic nulls as the satellites rotate. And again, a UHF preamp will help with this as it will make the nulls seem shorter.
If you have any questions, please ask. I miss home operations as I have moved and the new QTH is not satellite friendly (high horizons, lots of trees). I am hoping to be more active as a portable op again in the near future. Some of my previous ops if interested:
https://www.qrz.com/db/N4UFO/POh, by the way, I helped get an Elk antenna donated to a neighboring school to use with a SARCTRAC rotor system that they built as part of a robotics class. For a while SARCTRAC seemed to be shut down due to parts shortages... glad to see them back in production. If only I had the spare funds.

EDIT: They seem to be currently sold out.

P.S. I used to have an FT-847 for satellite operations. If using the original hand mic on SSB, I recommend upgrading to a condensor mic (Technofix makes a nice one). Also, the FT-847 has an internal preamp you might want to turn on ("INT"). OR the 847 can provide 12V up the feedline for a masthead preamp, but I powered mine separately and had both turned on.
73 & GL! Kevin N4UFO