op return – What are the mean, median, range, limits and trends in the size of coinbase transactions?

I’m attempting to estimate how much “spare capacity” there is for merged mining protocols.

As I understand it the scriptSig in the coinbase transaction must be less than 100B. However, the miner can include multiple OP_RETURN statements. For instance this recent block has a coinbase tx with 3 OP_RETURN statements and is 353 bytes.

A. Is there a limit in the overall size of the coinbase tx?

B. Is there a limit to the number of OP_RETURN statements in the coinbase transaction?

C. What is the mean, median, range and general trend in the size of coinbase transactions?

I’m attempting to estimate how much “spare capacity” there is for merged mining protocols.

As I understand it the scriptSig in the coinbase transaction must be less than 100B. However, the miner can include multiple OP_RETURN statements. For instance this recent block has a coinbase tx with 3 OP_RETURN statements and is 353 bytes.

A. Is there a limit in the overall size of the coinbase tx?

B. Is there a limit to the number of OP_RETURN statements in the coinbase transaction?

C. What is the mean, median, range and general trend in the size of coinbase transactions?