Funny, I honestly have more trouble with short pips because it is dead and fast and you have to loop back with a high enough arc to be sure you will clear the net.
And interestingly, against Long Pips, I like to give as much topspin as possible. Once I am into the rally I want to loop as often and as heavy as I can. With my serves I will mix them up to keep the pips player honest but I generally want them to give me as long and high an underspin ball as I can get from them so I can take the attack as early as possible which means a lot of fast topspin and dead serves. Once in a rally, I will only push or give underspin if I am forced to.
The reason for doing my best to not give underspin: my underspin is their topspin. Even if my push is low, a good pips player can attack that at will, and if instead they choose to give me a very short push, the push is still topspin and not as easy to handle as one may think. A good player can attack those short topspin pushes, but it is harder than looping long-high underspin at least if you want a high quality attack.
The reason for the consistent topspin attack is two- fold. If you have enough topspin, you can overpower them and make them hit long. Heavy topspin is much harder for them to keep down and if they can keep it on the table, you have more of a chance to get a higher weaker shot from them to kill. Now a pips player who is at a higher level than you will be much harder to play. But if you are looping heavy, you just have to be able to handle the fact that their underspin will be heavier. And the more spin they put on the ball, the more spin your loops will have. That part will all boil down to whether you can loop better than your opponent can chop. If you can keep looping, your spin will overpower his chop. But if his chop is better than your loop, your are going to be in trouble no matter what you do anyway.
The other reason for this strategy: your underspin is his topspin. Unlike with smooth rubber, with Long-Pips, an underspin ball is easy to handle and do a variety of things, especially attack with. If you watch the top pros, when they play Joo Se Hyuk, if they are forced to give him a push, he generally kills it.
Heavy topspin is much more of a challenge to control for a long pips player than anything else. So your best bet as your skills improve is to keep working on looping underspin. Powerful topspin backs them up, makes it more likely that you will get a higher ball and limits what the pips player can do with his long pips. For them to give you topspin against your loop, they have to flip their racket to the smooth side.