Collar Bolts Calculations for Tubesheets With Higher Allowables

Hye guys, I've been encountering a problem regarding collar bolts calculations. . .
Basically, I couldn't provide full threading in bolt holes of tubesheets, So I gave a proposal of collar bolts to my client. Client accepted the proposal. Then we followed the common standard already followed in previous projects for collar bolts, as per that standard 25% of total bolts will be collar bolts just for the seating of gasket during dismantlement of channel side.

Again client accepted the quantity. but now suddenly client wants me to provide the calculations for the seating area of the collar bolts. I've performed some calculations, and frankly speaking bolts are not passing.

Now the important point is, I've increased the allowable stress of bolts, equal to hydro test allowables (1.3 times of the bolt allowable stress) and clear the bolts. But client didn't accept my proposal, I've given them the reference of 'App. S of ASME section VIII Div.1' as well, but they didn't accept. Suggest me something, how to convince my client for using higher allowables, coz collar bolts will be used only for the dismantlement of the channel side at ambient temperature, by keeping the shell side in contact . . .

Need help !!