Glad the 16x4W worked, Richlstubbz. My Saito 91 liked that prop for hover and climbout, but got bogged down to 8800rpm and wouldn't climb at all in KE> so watch for that.
As far as your hovering question, I think that 130mm (empty tank) should be fine- its within the build instructions 20mm range & I've flown like that. Just make sure you land quick if it gets squirrely as the tank runs down: the CG actually moves back during your flights as the tank empties. Figure ~.86 oz weight per oz of 10% nitro fuel or 0.90 oz wt. per oz of 20% fuel. So you can see that maybe 10 or more oz change in your tank will change the CG a lot, especially with the stock tank location. I guess that's why the discriminating flyers put the tank on CG!
A coupla tricks for the hover- step zero being that "waterskiing prop" you found- first try it nice and high near the end of the tank (tail heavier) it should settle in better than full tank performance.... second, I found that I was over controlling in hover, and did much better on low rates at "factory" throws. Each plane has its own unique characteristics as it tries to flop out of hover. Oh, one other thing with that rockin' ST90 you should be able to set the throttle to slight climb, and things stabilize a lot while you get the hang of what to do when. Then slowly use less and less throttle until (someday years from now if you are like me) you are eventually doing a tailslide!!!!

One other trick I noticed when Andy Jesky did a demo at our field a coupla years ago: he was blipping the throttle constantly (maybe 10% up and down from hover throttle) during his nose-up manouvers. I think that the little puffs of thrust helped the surfaces work better for control. But then, he has quick reactions because he's younger.... so this trick may help you better than it does ME!! I do find myself using this throttle trick on my foamie, but on the Phoenix Extra, not so much. My Saito isn't all that responsive on throttle, so I tend to pick a setting for hover and then chase it with the other controls.