A much simpler way is to use spacer on headshell. Irrespective of how you increase the weight at cartridge end, you need to increase counterweight weight.
Try a simple experiment with commonly available items. I measured the weights of coins and they're as follows - 50 paise is 3.76 grams, one rupee is 3.78 grams, two rupees is 4.84 grams and five rupees bronze is 5.96 grams.
Let's assume your current cartridge is 6 grams. Add a two rupees coin to headshell end - let it just stay on top of headshell. Now move your counterweight to see if it can still balance with the added weight. Your total weight is 10.84 grams. Let's assume further that it is able to balance it with the added weight. Now check if there is room to increase the weight at the counterweight end for the tracking force. Let's assume that your cartridge has tracking force of 1.5 grams. Try adding the additional 1.5grams at counterweight (by moving weight closer to pivot).
You actually need 8.5 grams (DL 103 mass) minus your current cartridge weight = 2.5 grams. I don't know if you can get this exact weight to make your experiment more accurate. If the experiment is successful, you can try the 103 in your arm, but it won't be optimal. Later you can add spacer and heavier counter weight to increase effective mass.
Try a simple experiment with commonly available items. I measured the weights of coins and they're as follows - 50 paise is 3.76 grams, one rupee is 3.78 grams, two rupees is 4.84 grams and five rupees bronze is 5.96 grams.
Let's assume your current cartridge is 6 grams. Add a two rupees coin to headshell end - let it just stay on top of headshell. Now move your counterweight to see if it can still balance with the added weight. Your total weight is 10.84 grams. Let's assume further that it is able to balance it with the added weight. Now check if there is room to increase the weight at the counterweight end for the tracking force. Let's assume that your cartridge has tracking force of 1.5 grams. Try adding the additional 1.5grams at counterweight (by moving weight closer to pivot).
You actually need 8.5 grams (DL 103 mass) minus your current cartridge weight = 2.5 grams. I don't know if you can get this exact weight to make your experiment more accurate. If the experiment is successful, you can try the 103 in your arm, but it won't be optimal. Later you can add spacer and heavier counter weight to increase effective mass.