I think most of the other operators on here have made the point that 4m SSB will not be very lucrative. I have done an activation using the band and mode, but it was during a contest - so not particularly a fair representation!
If you want a good 4m antenna for SSB that is light and easy to erect, then I will suggest this as your best bet
I have made the 6m variant as well, both from Steve's website (GW7AAV), both work well.
How do I get SSB on the hill?
In the past I used a Spectrum Comms transverter for the job with the 817 on 2m as the IF. However I have since purchased a Ukrainian transverter and have been really pleased with the results, for the money you cant go far wrong - the IF is on 10m this time.
FM on the other hand, is a far better prospect. This is the mode I use for 4m when doing SOTA, however I never purely rely on it to get me the 4 QSOs, that said on a Saturday/Sunday in Welsh Border/North Wales/South Wales you will work lots of people. I have always combined it with 2m SSB or 2m FM as they're generally reliable band/mode combinations.
The beauty of FM is that lots of radio amateurs in the UK have an old converted PMR rig on their shelf and it is normally on all the time, sat on 70.450MHz with a dipole connected. They normally don't hear that much activity, so when they do, they more than often come back to the call. This certainly is what I have expereinced in the 7 years I have been activating. Last Saturday 13/05/17 I managed 11 QSOs at around 1000 from G/WB-004 all on 4m FM
With VHF/UHF it all depends on the time of day and of course the day of the week you activate.
Rig wise for FM - Gerald has hit the nail on the head with the Wouxun KG699e - Mine has had the battery upgrade to 1700mAH, no noticeable weight difference. It is tough little rig and has been with me since the start of my SOTA activations. The antenna is nothing more than a Slim Jim that I made 7 years ago, I have serviced it about 2 times, checking the coax for connections to the ladder feed, checking for water ingress into the braid of the coax and then do an SWR check before re-sealing the coax. It seems to work really well and takes about an hour to make the thing!
This is the design I use - http://www.summits.org.uk/tiki-index.php?page=4m+J-pole
Here are the top 25 Activators in the World - I think Barry M0IML and I are going to struggle to make it to the top spot!
Barry and I used to use the band alot, he moved away to Kent so his activations have become less, I got lazy after getting MG so my activations have got less!!
Well worth a go, but the key is to pick the day and time and take a backup 2m radio IMHO
The other way is to get your hands on one of these hen's teeth rigs http://www.cqhq.co.uk/2011/07/wouxun-kg-uvd1pl-2m4m-dual-band-review.html
If you spot for 4m FM or SSB I can try to work you from home, have 50 watts on both modes and a vertical for FM and a 4 ele beam up at home for SSB.
73 and Good luck -