What do you already have for features? What is the level of riding in your parks? Also what are you working with HDPE?
If you didn't have any boxes I would build at 2 small low 8'- 12'boxes, 2' 16'-20' boxes. Not that exciting but those are going to be your most hit feature. A flat box isn't as exciting as a quad kink but I'll see people hiking a flat box all day working on tricks, everyone noob to sick can get down on them. Also would def build 2 so you can have a down box and a flat box. Also can make it an up, or run a down flat with one of the small ones and still have another small one for noobs.
Mellow flat down box around 8'x16'up to maybe 12'x22' depending on who you're building it for. That's a nice feature especially on the smaller end. Everyone can hit it pretty easily and changes it up away from just the flat box, you can disaster it etc.
Aframe boxes are pretty solid. MAybe a 12'x12 not TOO steep. If the riding level is lower, a lower one maybe 10'x10'
I personally like battleships a lot but they're popularity is hit or miss these days and they use a lot of materials. Not saying don't make one but make sure it's what you want. Also depending on the size they get huge pretty fast, make sure you have the means to move it around.
Also try to very your widths a bit. On most of them I wouldn't go wider than 1'. That's a good size and slides nice. For the beginner stuff you can go wider. Maybe even build a dance floor if you have that much top sheet to spare. You can do one of the flat boxes narrower almost rail size to work as a stepping stone for getting people from the wider boxes to the flatbar rails.
What do you have for rails? do you have a decent assortment of different sized flat rails? Some super noob sized ones and some bigger ones you can use as flats, ups, downs, and combos like closeouts etc. Again not the most exciting features but very useful.
Hows the mix of rail types. Do you have some flat bar, some skinny tubes, some fat tubes and maybe a shotgun or 2? Nice to have a mix.
A DFD rail is always a a big one. You kind of need a good dfd these days. I would go at least 12' on the downs because 10 or less is too short imo. Also mellow kinks are awesome. Just my opinion but I like df kinks at 12.5. You can go steeper but I've seen skiers skipping the dicks on rails that are steeper, and people just surviving some of the steep dfds etc. I like more length and less angle. It slides nice and smooth, it's long enough to trick and feel comfortable but it's also mellow enough to trick. You can have a 30+ dfd feel less sketchy than a 20' that's short and steep.
Variety is everything but make sure you have the basics down. You don't want to waste all your material on something huge like an sbox right now. S boxes are sick, quad kinks are sick, but the basics are what's going to get hit the most. Having at least 4 flat boxes and flat rails is pretty much a necessity for any mountain.
Just think through the size of everything. Think through the angles of the kinks. You don't want to have a rail that looks like this and ate up your budget
Idk. That's just my $.02
Stoked to hear you got some materials and are building some new features, best of luck.
