You say that using decimal indices requires more precision with deck estimation. The opposit is true.
Assuming my indices are correct, deck estimation is in fact the only source of error remaining in my system.
Let's take the case 8v5 with an index of +3.5 (another in-betweener).If there are 4.5 decks remaining with an RC of +18, the TC is exactly +4.So an I18 user will also find the right play (double), but only if he estimates correctly at half deck precision.However,many people including myself don't like to divide by 4.5 and will be tempted to round up to 5. Now the TC has dropped to +3.6 with the result that the I18 user will miss the right play.But my decision has not been affected.
So you see that the decimal indices allow a greater tolerance in deck estimation.

Francis Salmon