Relinquishment / release deed in maharashtra. genuine issue.

Dear members,

Greetings!

I have to register a Relinquishment Deed, wherein:

(In this case, F = Father | M = Mother | S = Son | D = Daughter)

1.  The F and M jointly purchased a flat by virtue of a registered Agreement to Sale.
   
   
2. Govt. value at time of registration was 10 times lesser than the present market value.
   
   
3. Stamp Duty paid on the Agreement to Sale, on Govt. value.
   
   
4. The property is self acquired, and lies in Maharashtra – in urban area.
   
   
5. F died intestate leaving behind his M, S and D.
   
   
6. Conveyance Deed is pending to be registered.
   
   

Consequent upon the death of F:

1. When F was alive, the share in the entire property was 1 (F) : 1 (M)
   
   
2. Now, will the share will be 1 (M) : 1 (S) : 1 (D)? (According to the builder's advocate it has to be so)
   
   
3. Or will it be 2 (M) : 1 (S) : 1 (D)? (According to the M, S, & D this will be ideal, as all 3 are legal heirs to F)
   
   
4. The Conveyance Deed is still pending for registration on this point, as the share distribution is disputed by the builder's advocate.
   
   
5. First step, Conveyance Deed to be registered, bringing S & D on record, as the legal heirs.
   
   

Now:

1. S & D wish to release and relinquish all their shares each in the said property in favour of M, without any monetary consideration.
   
   
2. The Stamp Duty on Conveyance Deed need not be paid as it is already paid while registering the Agreement to Sale.
   
   
3. Second step, register a Deed of Relinquishment. Builder says 75% of the true market value needs to be paid for the stamp duty in this case; which I don’t find correct.
   
   
4. I perused the Bombay Stamp Act, 1958 with the latest amendments, according to Article 52 of which: “RELEASE, that is to say, any instrument (not being an instrument as is provided by section 24) whereby a person renounces a claim upon other person or against any specified property, (a) if the release deed of an ancestral property or part thereof is executed by or in favour of brother or sister (children of  renouncer's parents) or son or daughter or son of predeceased son or daughter of predeceased son or father or mother or spouse of the renouncer or the legal heirs of the above relations. --- Two hundred rupees. (b) In any other case. --- The same duty as is leviable on a conveyance under clause (a), (b), or [as the case may be (c)], of Article 25, on the market value of the share, interest, part or claim renounced.”
   
   
5. Obviously, provision (a) is inapplicable here as it is a “self-acquired property”.
   
   
6. Further, studying Article 25, it appears that for Urban Areas, only 5% of the market value will be applicable.
   
   
7. Builder says; 75% of present market value will have to be paid in any case. His office is compulsorily arranging the registration process for Release Deed also which actually is not necessary.
   
   
8. He also shows a printed booklet wherein the Article 25 says 75% in the urban areas. Says my Bare Act is outdated.
   
   
9. Till that amount goes to the builder, the things are on hold.
   
   

Are the members aware if any such amendment was really carried out? What could be the silent way out in this case? The parties want to avoid clashes with the builder. Suggestions please.

Thanks in anticipation. God bless you all.