No one ever gets ideal haha, a strong horse would do just fine. If youve ever felt the weight of some of the roping saddles that the cowboys use, with the riders that are generally the same weight as you it would probably come out to roughly the same weight as all your gear. They commonly ride smaller horses who never have a problem with the weight. Those horses never have a problem and they are very active.
Things must have REALLY changed in the last 30+ years since I last worked with cattle. Our heaviest rider, with saddle, tack and rain gear was under 250.
If someone is really working cattle they don't tend to put on much weight
. Even at 5' 9" is was consuming over 3,000 calories a day. E.g. If leaving from home my breakfast was 4-6 egg and cheese omelette, 2 biscuits (or toast if I had to make it
) with jam, roughly a 1 lb steak (generally a rib steak) or slab of ham, enough cheesy grits to cover 1/2 the plate (omelette on top) and a couple of mugs of hot tea.
That was our second largest meal of the day (nothing competed with supper) and I still never topped 150 lbs unless it was a very cold day and I was wearing a lot of heavy clothes. Granted, my taller cousins weighed more. Tallest was 6' 3", just as then, but being taller he weighed a little more. Working cattle was a physically demanding job and you just didn't put on much weight. One of those things you look back on with (sometimes) fond memories (a bit like boot camp), but NEVER want to do it again
. Mending fence, moving uncooperative cattle, castrating, finding them when they get out and getting them back, etc, etc, etc, the work never ended and if a cow can find a way out it doesn't care that it's Christmas day or that you had plans, or that there's freezing rain.
I've gotten off topic
First, keep in mind that while we do ride them and they can manage it, nature did not design the horse to carry a load on it's back. If you look at the physical design of the horse it's built like suspension bridge with no supporting cables (wouldn't advice crossing one designed like that).
If you're going to jump with that much weight (don't care how big your horse is) worry about everything from the knees down. Those are the places most likely to have a point of failure and your going to want large and dense cannon bones. You'll also what to work with your horse on jumping so that it will be better at it and in better condition for it. Remember that immediately after the foot first makes contact, for a moment, the horse is going to have most of it's weight along with what it's carrying suddenly delivered and concentrated on those two legs while landing from whatever height it's coming down from. Put on a back pack with 150 lbs of gear, tie a metal plate to your foot (if they're shod) slip on flip-flop (if they're booted) or go bare foot (if they're unshod), climb a step ladder up to about 4 feet, hold up foot up, jump off and land on just one foot (and don't bend you knee...your horse won't....to lessen/absorb the impact). It's not an exact comparison (tougher to simulate the amount of forward momentum the horse will have), but you're landing on the same % of weight baring limbs, carrying the extra weight and landing from a height. Of course the human skeletal structure is better designed for this, but it's tough to make everything an exact comparison between animals that nature designed differently.
I'll go with MyBoyPuck here. For the odd downed tree that you might encounter and can't step over or go around I'd dismount. It's always better to be safe than sorry. An injured horse is not fun to deal with at home. It's even worse when you're out in the middle of no where in a situation that you might not be able to get help for the horse.
As morbid as this is going to sound (and heaven forbid that it should, but it has/does happen) if you do have an injury at a remote location that's severe, a lot of suffering and you need to put the animal down make sure you use a high enough caliber to easily pass through the skull and DON'T shot between the eyes (you just blow out their sinus). About half way between an imaginary line between the eyes and an imaginary line between the ears is where their brain is. Yes, I know it's a terrible topic, but I promise you it's better to know how to do it right if you have to then find yourself having to and do it wrong and having to live with that memory of what it was like doing it wrong added to an already bad experience of putting you mount down.
Not my horse though, so it's not my call. Everyone has to what works for them (and hopefully the horse).