I have drilled every Rotogrip ball (hence the name Roto4ever) for me and my friend and we have every ball made in the past 3 years. I do not have a Pluto but drilled one for my friend the very way you describe. This is by far the weakest ball RotoGrip has ever made, even the Neptune (same core, pearl cover) hooks more than the Pluto. So this should fit well for you when the lanes break down. It does need dry boards though to recover so keep that in mind. I personally have 2 Cells, one 4 x 4 and one 5 x 3. The first one 4 x 4 is an all around great layout for this ball and when I first drilled it, I could go from 1st game to 3rd game with this in league. The Cell does take some maintenance to keep it in top shape, but what ball doesn't these days. I believe this layout is the first one in the drill sheet that comes with the ball so you should be able to drill it no problem. Rotogrip makes some good stuff, I'm going back to Storm myself because nothing Roto has now, besides the Cell, looks good to me. The current Storm balls do though. I tried an Illusion and I think I drilled it wrong and it never did what I thought it would do and I'm not impressed with the Grand Illusion. For my money, the original Horizon pearl, Horizon solid were far better balls.
By the Way, tell your pro shop guy to try some different layouts and get with the times.
Good Luck.
Roto4ever