I've done this with a Briggs, no reason it won't work with the GXH. The connecting rod has a dipper on it. It sort of force feeds the rod, and throws oil around for everything else. There is no pump and the key is oil level in relation to the crank centerline.
With the engine on a bench, use a level and scribe a mark under the crank that represents the oil level when full. Measure it, tilt the engine to the desired degree you want, and mark under the crank where you need the oil. Keeping the engine tilted, use the level again and scribe a line for the oil level back toward the filler. You can now measure down from the filler to that line and know how much oil you want to maintain in the crankcase. You can build yourself a longer dipstick, ir just make something to measure with. The only "hangup" is that you have to hang the front of the bike in the air to change the oil in the Honda.
