For HF SOTA you can’t beat a simple dipole set up as an inverted V. It’s what a lot of activators use. Cut a dipole for your favourite band. No need to use thick wire. Support the centre with a fibreglass fishing pole, add some fishing line to the ends and peg out. Feed with speaker wire and a small balun at the rig or just thin co-ax. For more than one band add some links - see John GW4BVEs pics
Mine winds up onto a ply winder and weighs 250g. It covers 5MHz to 50MHz. I use the pole as a walking stick!
ANY shortened, coil loaded antenna is going to be very inefficient on HF and if you’ve only got 5W, you really don’t want to use 4.9W just to heat up that coil! A dipole is much more efficient.
An antenna that looks big at home is surprisingly small when you get out on the hills. The only summit I’ve activated so far where there wasn’t really room for it was Yr Wyddfa (Snowdon) - it was busier than Picadilly Station on a bank holiday and I didn’t want to garrotte any grockles.
Give it a try!
73 & Good luck.