First, your Ping shafts are most likely .355 taper tip, so you can’t trim anything from the tip. If your irons are Ping, and I am assuming they are, the only shafts you can use must be .355 taper tip. If you install 7 iron length taper tip shafts into the 8, 9, PW, etc., trimming all to the 7 iron length, the 8, 9, PW etc. will play progressively more flexible because of the head weight progression. Single length irons require the head weights to be all the same for the shaft flexes and swing weights to be the same at the designated single length. Also, in my opinion, making your shorter length irons longer does not make them easier to hit. Suggestion is to have a qualified professional take a look and see if he can help you with your ball striking issues. I would definitely try that before making such a change in my club lengths. It may be that single length clubs could work for you, but they should be proper single length clubs with the head weights and shafts that make that type of set playable.