Thanks guys, those are definitely helpful points which I wasn't aware of.

I have managed to get the tilt working, though only in a trouble-shooting state. While I think this rules out Hydraulic problems, I need help understanding where I should look next, considering the conditions. I got Tilt Forward to operate by moving the Parking Brake Solenoid (SV2) electrical leads and attaching them to the Tilt Lockout Solenoid (SV1). When wired this way and the Parking Brake switch is DISENGAGED (OFF, no brake), the Lift Tilts Forward when the tilt lever is activated.

With Key on and seat switch closed:
- Engaging/disengaging the tilt lever does not affect the voltage readings on the SV1 leads, they read +10V positive lead, -26V Negative lead. If it needs to be energized to allow tilt, it should be working. If it needs to be NOT energized to allow tilt, it should be working when unplugged, which it does not... (either entirely unplugged, or with just the +10V unplugged and the -26V still plugged in). That's weird because I would think that replicates the condition it gets from the parking Brake wires when it is working.

- Disengaging the Brake switch (to "OFF") provides +10V between the smaller positive lead to chassis ground, the larger negative lead remains at -26V to chassis ground. Engaging the Brake switch (to "ON") removes the +10V, on the smaller positive lead, leaving 0v to chassis ground, and the larger negative lead remains at -26V to chassis ground. From this I would confirm that logically, the Parking Brake is on without being energized and off when energized.

(To me, these +10V / -26V readings don't seem very straight-forward, I expected +36V / 0V, but I assume the system is designed that way, it clearly adds up to the required 36V. All the switches at the levers/spool controllers for Raise, Shift, Tilt read the same (+10V on the common supply wire to all switches, and -26V on each accompanying switch lead). If this is wrong I'm sure you will let me know!

I learned that:

-Tilt forward is the only function which is not performing. (The unit was tilted all the way back). Tilt back seems to work regardless, even when there are no leads attached to Tilt Lockout Solenoid SV1.

-Tilt Lockout Solenoid SV1 and Parking Brake Solenoid SV2 are both marked "HYDRAFORCE 36V" and look identical, but have slightly different numbers embossed:
Tilt Solenoid: 4300098 2509
Brake Solenoid: 4300098 2616

-Both solenoids test at 88 ohms impedance when measured negative post to positive post, and around 10 ohms when measured positive post to negative post. The manual indicates 88 ohms is in spec and that they are polarity sensitive with suppression diodes, but doesn't specifically say to test it backwards to get the 88 reading. Since both test the same and
the parking brake functions fine, I assumed this is OK and means the solenoids are both fine.

-The Tilt Limit switch and Mast Height Lockout switch seem to be working correctly. Tilt Limit switch prevents mast from going to second stage, and mast above first stage prevents tilt from working.