Robert, the best thing I can advise you to do around the NH balewagons for inspection is to tell the sales guy to go powder his nose, 'cuz you're going to be there awhile.

Start at a corner of the machine. Pick a corner, any corner. Look at ALL the steel for cracks. Look at EVERY mount point for a hydraulic ram. Look over every hose, every steel line. Just work methodically from one corner, up one side of the machine, around/under the front or back, then down the other side.

I've owned two (1075 and 1095) and I used this technique to inspect the balewagons between every cutting for cracks and problems. It takes me about one hour to 90 minutes to closely inspect everything on a wagon I've never seen, 30 minutes on a wagon that I've been operating and one where I know the "personality" of the machine. One machine I inspected this way caused some real heartache for a dealer - a mechanic got severely chewed out and I think a salesguy got let go after I exposed what a basket case a particular 1095 was; air filter was never changed, cracks in the frame, one of the main table rams had been punched through the main table, cab had nearly fallen off and been re-welded... all that abuse in about 3000 hours. They wanted over $60K for that machine and I told them I might, maybe... with more evaluation... give them $40K on the machine, because it was going to need a lot of TLC.

On a SP machine, pay special attention to the frame rails forward of the front axle. That cab is catilevered out in front of that front axle, and on rough ground, I've seen the cabs break their rails off just in front of the first table. On 1095's, no less.

First and best place to look for problems is around the spring packs. Examine the frame rails closely from about 2' behind the spring mounting points to about 2' forward. If someone has been playing balewagon NASCAR across ruts and ditches, you'll see cracking around the spring mounting points. Look from the bottom of the frame rail upwards, inside and out. Check for new paint around these areas: if you need new paint on the frame rails, stroll away from that machine in a rapid manner.

Check the hinge points for all the tables, esp. the main load rack. Look for welds. 

BTW - welds done properly aren't something I would have issue with. It is when someone has wailed the snot outta the machine, the rail has unzipped 75% of the way up the rail, the start of the crack has opened up and now the rail is twisting from nearly being severed - that, I have a problem with. If someone spotted a crack starting, it was only 1/2" to 1" long, and they got on it right away - that's not too bad. When the cracks get long on those C-channel rails, the uncracked steel starts to flex and twist, and it quickly will start to stress in ways you can't fix with welding.

Oh - and if you come across a SP wagon that has had the Mil-stack big bale claw on it? Walk away. I've seen three of these wagons (all 1095's) where that Mil-stak thing has stressed the front end and the right rail so badly that in 2000 hours, the machine looked like it had 8000 hours. Not good. Just don't mess with any machine that's been hacked on for big bales.  You need a reliable machine for 2-string bales. There's so machines out there, you don't need to adopt a basket case.