For 39: stack it on the block so it starts toppling left, put a peg on the left smiley so it pushes the blocks right, place the horizontal plank on the bottom smiley and block (it'll push any obstacles up), then use the /| triangle as a stopper on the right. It's a little tricky, but not nearly as hard as it seems.
ps, currently you can beat the whole game by wielding dual repeating rifles. Add a dodge-switch for one if you want to finish with more health. In the future it would be cool if some levels allowed multiple switches.
To get the skids, just find the place where a turn is wide with trees splitting it into two. You can skid in circles after a bit of practice and you can easily score a 200. You'll still have enough time to finish the race in time.
for challenge 5, the key is lowering the smog (ie, upgrade to natural gas, dont' use coal plant), and get the resources going asap. After the first night it's easy.
I hope there's an anti tank call. I just bunker up and keep calling arty till it's dead. Bombs seem practically useless because it just lands on one random spot, would be nice if you could designate a target.
Antennas suck, they end up dying so fast, especially now with Mortar getting added. The key is to train your signaller up to 15xp, at that point his call time will be tolerable and you'll actually be able to intercept planes and respond to waves in time.
AAAs suck. I'm averaging 80 waves per game now. The key is to get units that'll last long, so get tanks and people. People can hide in bunkers when an enemy tank comes out (bunker them and let your signaler arty until the tank is dead), and your tank has enough HP to withstand arty/enemy explosives beatings. Jeeps and AAAs are useless because they'll probably die after the first explosives encounter.
santa badge says you get free range training, but i didn't cash mine in (it's not bs tho). you can't actually target him, which makes killing him hard, you have to arty or nade him by accident.
I found a way to hack the quality. Reload the game, then quickly press right over the flash area. If the typical flash menu doesn't come up, hit right again until you get a flash menu. If you do it before MNB2 loads, you'll have an option to change Quality. Have the menu open and wait for MNB2 to load, then change the quality and it'll be set.