Hi RD42,
I was a bit confused by your dosage, you initially say,
"I'm on 2 25/100 Sinemet 4 times a day", ie 8 tablets per day, but later say,
"6 x 25/100 per day".
The typical starting dose is usually 3 x 25/100 tablets, and this tends to increase as the disease advances. You don't say how long you have had PD, but many contacts diagnosed 10 years or more ago progress to around 6 to 8 tablets per day. I have seen figures of 12 x 25/100 quoted as the max dose, yet a PD friend was taking 23 tablets (2,300mg L-dopa), before he died of non PD related causes.
I agree with Lindy, adding entacapone enables you to reduce your intake, by extending the on time. It is better to take this as Stavelo, since it is more intimately mixed. Bear in mind that higher dosages are building up trouble ahead with dyskinesia.
Hope this helps.
Ron